Digital camera
Encyclopedia
A digital camera is a camera
that takes video
or still photograph
s, or both, digital
ly by recording images
via an electronic
image sensor
. It is the main device used in the field of digital photography
. Most 21st century cameras are digital.
Digital cameras can do things film cameras cannot: displaying images on a screen immediately after they are recorded, storing thousands of images on a single small memory device, and deleting images to free storage space. The majority, including most compact cameras, can record moving video
with sound
as well as still photograph
s. Some can crop
and stitch
pictures and perform other elementary image editing
. Some have a GPS receiver built in, and can produce Geotagged photographs.
The optical system works the same as in film cameras, typically using a lens with a variable diaphragm
to focus light onto an image pickup device. The diaphragm and shutter admit the correct amount of light to the imager, just as with film but the image pickup device is electronic rather than chemical. Most digicams, apart from camera phones and a few specialized types, have a standard tripod screw.
Digital cameras are incorporated into many devices ranging from PDA
s and mobile phone
s (called camera phone
s) to vehicles. The Hubble Space Telescope
and other astronomical
devices are essentially specialized digital cameras.
s, operated as a mobile application through the cellphone menu. Professional photographers and many amateurs use larger, more expensive digital single-lens reflex camera
s (DSLR) for their greater versatility. Between these extremes lie digital compact cameras and bridge digital camera
s that "bridge" the gap between amateur and professional cameras. Specialized cameras including multispectral imaging equipment and astrograph
s continue to serve the scientific, military, medical and other special purposes for which digital photography
was invented.
" uses. Hence, they are also called point-and-shoot cameras. The smallest, generally less than 20 mm thick, are described as subcompacts
or "ultra-compacts" and some are nearly credit card size.
Most, apart from ruggedized or water-resistant models
, incorporate a retractable lens assembly allowing a thin camera to have a moderately long focal length
and thus fully exploit an image sensor larger than that on a camera phone, and a mechanized lens cap to cover the lens when retracted. The retracted and capped lens is protected from keys, coins and other hard objects, thus making it a thin, pocketable package. Subcompacts commonly have one lug and a short wrist strap which aids extraction from a pocket, while thicker compacts may have two lugs for attaching a neck strap.
Compact cameras are usually designed to be easy to use
, sacrificing advanced features and picture quality for compactness and simplicity; images can usually only be stored using lossy compression (JPEG
). Most have a built-in flash
usually of low power, sufficient for nearby subjects. Live preview
is almost always used to frame the photo. Most have limited motion picture capability. Compacts often have macro
capability and zoom lens
es but the zoom range is usually less than for bridge
and DSLR
cameras. Generally a contrast-detect autofocus
system, using the image data from the live preview feed of the main imager, focuses the lens.
Typically, these cameras incorporate a nearly silent leaf shutter into their lenses.
For lower cost and smaller size, these cameras typically use image sensor
s with a diagonal of approximately 6 mm, corresponding to a crop factor
around 6. This gives them weaker low-light performance, greater depth of field
, generally closer focusing ability, and smaller components than cameras using larger sensors.
Starting in 2011, some compact digital cameras can take 3D still photos. These 3D compact stereo camera
s can capture 3D panoramic photos for play back on a 3D TV. Some of these are rugged and waterproof, and some have GPS
, compass, barometer
and altimeter
.
to frame the image. Their autofocus
uses the same contrast-detect mechanism, but many bridge cameras have a manual focus
mode, in some cases using a separate focus ring, for greater control. They originally "bridged" the gap between affordable point-and-shoot cameras and the then unaffordable earlier digital SLRs.
Due to the combination of big physical size but a small sensor, many of these cameras have very highly specified lenses with large zoom range and fast aperture
, partially compensating for the inability to change lenses. On some, the lens qualifies as superzoom
. To compensate for the lesser sensitivity of their small sensors, these cameras almost always include an image stabilization
system to enable longer handheld exposures.
These cameras are sometimes marketed as and confused with digital SLR cameras since the appearance is similar. Bridge cameras lack the reflex viewing system of DSLRs, are usually fitted with fixed (non-interchangeable) lenses (although some have a lens thread to attach accessory wide-angle or telephoto converters
), and can usually take movies with sound. The scene is composed by viewing either the liquid crystal display or the electronic viewfinder
(EVF). Most have a longer shutter lag
than a true dSLR, but they are capable of good image quality (with sufficient light) while being more compact and lighter than DSLRs. High-end models of this type have comparable resolutions to low and mid-range DSLRs. Many of these cameras can store images in a Raw image format
, or processed and JPEG
compressed, or both. The majority have a built-in flash similar to those found in DSLRs.
In bright sun, the quality difference between a good compact camera and a digital SLR is minimal but bridgecams are more portable, cost less and have a similar zoom ability to dSLR. Thus a Bridge camera may better suit outdoor daytime activities, except when seeking professional-quality photos.
In low light conditions and/or at ISO equivalents
above 800, most bridge cameras (or megazooms) lack in image quality when compared to even entry level DSLRs. However, they do have one major advantage: their much larger depth of field
due to the small sensor as compared to a DSLR, allowing larger apertures with shorter exposure times.
A 3D Photo Mode
was introduced in 2011, whereby the camera automatically takes a second image from a slightly different perspective and provides a standard .MPO file for stereo display.
or on the rear LCD. These are simpler and more compact than DSLRs due to the removal of the mirror box, and typically emulate the handling and ergonomics of either DSLRs or compacts. The system is used by Micro Four Thirds, borrowing components from the Four Thirds DSLR system.
s (SLRs). They take their name from their unique viewing system, in which a mirror reflects light from the lens through a separate optical viewfinder. At the moment of exposure the mirror flips out of the way, making a distinctive "clack" sound and allowing light to fall on the imager.
Since no light reaches the imager during framing, autofocus
is accomplished using specialized sensors in the mirror box itself. Most 21st century DSLRs also have a "live view" mode that emulates the live preview system of compact cameras, when selected.
These cameras have much larger sensors than the other types, typically 18 mm to 36 mm on the diagonal (crop factor
2, 1.6, or 1). This gives them superior low-light performance, less depth of field
at a given aperture, and a larger size.
They make use of interchangeable lenses; each major DSLR manufacturer also sells a line of lenses specifically intended to be used on their cameras. This allows the user to select a lens designed for the application at hand: wide-angle, telephoto, low-light, etc. So each lens does not require its own shutter, DSLRs use a focal-plane shutter
in front of the imager, behind the mirror.
chip, and a focusing mechanism. These cameras are almost solely used in industrial settings to capture an image of a constant stream of moving material. Unlike video cameras, line-scan cameras use a single row of pixel sensors
, instead of a matrix of them. Data coming from the line-scan camera has a frequency, where the camera scans a line, waits, and repeats. The data coming from the line-scan camera is commonly processed by a computer, to collect the one-dimensional line data and to create a two-dimensional image. The collected two-dimensional image data is then processed by image-processing methods for industrial purposes.
s. Other small electronic devices (especially those used for communication) such as PDA
s, laptops and BlackBerry
devices often contain an integral digital camera, and most 21st century camcorder
s can also make still pictures.
Due to the limited storage capacity and general emphasis on convenience rather than image quality, almost all these integrated or converged devices store images in the lossy but compact JPEG
file format.
Mobile phones incorporating digital cameras were introduced in Japan in 2001 by J-Phone. In 2003 camera phones outsold stand-alone digital cameras, and in 2006 they outsold all film-based cameras and digital cameras combined. These camera phones reached a billion devices sold in only five years, and by 2007 more than half of the installed base
of all mobile phones were camera phones. Sales of separate cameras peaked in 2008.
Integrated cameras tend to be at the very lowest end of the scale of digital cameras in technical specifications, such as resolution, optical quality, and ability to use accessories. With rapid development, however, the gap between mainstream compact digital cameras and camera phones is closing, and high-end camera phones are competitive with low-end stand-alone digital cameras of the same generation.
as an engineer at Eastman Kodak
invented and built the first digital camera using a charge-coupled device
image sensor in 1975.
of a digital camera is often limited by the image sensor
(typically a CCD
or CMOS sensor chip) that turns light into discrete signals, replacing the job of film in traditional photography.
The sensor is made up of millions of "buckets" that essentially count the number of photon
s that strike the sensor.
This means that the brighter the image at a given point on the sensor, the larger the value that is read for that pixel
.
Depending on the physical structure of the sensor, a color filter array
may be used which requires a demosaicing
/interpolation algorithm.
The number of resulting pixels in the image determines its "pixel count".
For example, a 640x480 image would have 307,200 pixels, or approximately 307 kilopixels; a 3872x2592 image would have 10,036,224 pixels, or approximately 10 megapixels.
The pixel count alone is commonly presumed to indicate the resolution of a camera, but this simple figure of merit
is a misconception. Other factors impact a sensor's resolution, including sensor size, lens quality, and the organization of the pixels (for example, a monochrome camera without a Bayer filter
mosaic has a higher resolution than a typical color camera).
Where such other factors limit the resolution, a greater pixel count does not improve it, but may rather make the digital images inconveniently large and/or exacerbate image noise
. Many digital compact cameras are criticized for having excessive pixels. Sensors can be so small that their 'buckets' can easily overfill; again, resolution of a sensor can become greater than the camera lens could possibly deliver.
Demanding high quality and resolution (e.g. for use in professional photography), this count is an object of manufacturer competition. As of August 2011, the highest resolution available on the market is 80.1 MP.
As the technology has improved, costs have decreased dramatically. Counting the "pixels per dollar" as a basic measure of value for a digital camera, there has been a continuous and steady increase in the number of pixels each dollar buys in a new camera, in accord with the principles of Moore's Law
. This predictability of camera prices was first presented in 1998 at the Australian PMA DIMA conference by Barry Hendy and since referred to as "Hendy's Law".
Since only a few aspect ratio
s are commonly used (mainly 4:3 and 3:2), the number of sensor sizes that are useful is limited. Furthermore, sensor manufacturers do not produce every possible sensor size, but take incremental steps in sizes. For example, in 2007 the three largest sensors (in terms of pixel count) used by Canon were the 21.1, 17.9, and 16.6 megapixel CMOS sensors.
Since the first digital backs were introduced, there have been three main methods of capturing the image, each based on the hardware configuration of the sensor and color filters.
The first method is often called single-shot, in reference to the number of times the camera's sensor is exposed to the light passing through the camera lens. Single-shot capture systems use either one CCD with a Bayer filter
mosaic, or three separate image sensor
s (one each for the primary additive colors red, green, and blue) which are exposed to the same image via a beam splitter.
The second method is referred to as multi-shot because the sensor is exposed to the image in a sequence of three or more openings of the lens aperture. There are several methods of application of the multi-shot technique. The most common originally was to use a single image sensor
with three filters (once again red, green and blue) passed in front of the sensor in sequence to obtain the additive color information. Another multiple shot method is called Microscanning
. This technique utilizes a single CCD with a Bayer filter but actually moved the physical location of the sensor chip on the focus plane of the lens to "stitch" together a higher resolution image than the CCD would allow otherwise. A third version combined the two methods without a Bayer filter on the chip.
The third method is called scanning because the sensor moves across the focal plane much like the sensor of a desktop scanner. Their linear or tri-linear sensors utilize only a single line of photosensors, or three lines for the three colors. In some cases, scanning is accomplished by moving the sensor e.g. when using Color co-site sampling
or rotate the whole camera; a digital rotating line camera
offers images of very high total resolution.
The choice of method for a given capture is determined largely by the subject matter. It is usually inappropriate to attempt to capture a subject that moves with anything but a single-shot system. However, the higher color fidelity and larger file sizes and resolutions available with multi-shot and scanning backs make them attractive for commercial photographers working with stationary subjects and large-format photographs.
Dramatic improvements in single-shot cameras and raw image file
processing at the beginning of the 21st century made single shot, CCD-based cameras almost completely dominant, even in high-end commercial photography. CMOS-based single shot cameras remained somewhat common.
Most current consumer digital cameras use a Bayer filter
mosaic in combination with an optical anti-aliasing filter
to reduce the aliasing due to the reduced sampling of the different primary-color images.
A demosaicing
algorithm is used to interpolate
color information to create a full array of RGB image data.
Cameras that use a beam-splitter single-shot 3CCD
approach, three-filter multi-shot approach, Color co-site sampling
or Foveon X3 sensor
do not use anti-aliasing filter
s, nor demosaicing.
Firmware
in the camera, or a software in a raw converter program such as Adobe Camera Raw, interprets the raw data from the sensor to obtain a full color image, because the RGB color model
requires three intensity values for each pixel: one each for the red, green, and blue (other color models, when used, also require three or more values per pixel).
A single sensor element cannot simultaneously record these three intensities, and so a color filter array
(CFA) must be used to selectively filter a particular color for each pixel.
The Bayer filter pattern is a repeating 2×2 mosaic pattern of light filters, with green ones at opposite corners and red and blue in the other two positions. The high proportion of green takes advantage of properties of the human visual system, which determines brightness mostly from green and is far more sensitive to brightness than to hue or saturation. Sometimes a 4-color filter pattern is used, often involving two different hues of green. This provides potentially more accurate color, but requires a slightly more complicated interpolation process.
The color intensity values not captured for each pixel can be interpolated (or guessed) from the values of adjacent pixels which represent the color being calculated.
s that are smaller than the typical 35mm film size has a smaller field or angle of view
when used with a lens of the same focal length
. This is because angle of view is a function of both focal length and the sensor or film size used.
If a sensor smaller than the full-frame 35mm film format is used, as in most digicams, then the field of view is cropped by the sensor to smaller than the 35mm full-frame format's field of view. This narrowing of the field of view is often described in terms of a focal length multiplier or crop factor
, a factor by which a longer focal length lens would be needed to get the same field of view on a full-frame camera.
The result is geometrically similar to taking the image from the film camera and cutting it down (cropping) to the size of the sensor, ignoring various questions such as resolution. For moderately large DSLRs the crop factor may be in the range of 1.3-2 while smaller cameras use smaller sensors with a larger crop factor.
If the digital sensor has a higher or lower density of pixels per unit area than the film equivalent, then the amount of information captured differs correspondingly. While resolution can be estimated in pixels per unit area, the comparison is complex since most types of digital sensor record only a single colour at each pixel location, and different types of film have different effective resolutions. There are various trade-offs involved, since larger sensors are more expensive to manufacture and require larger lenses, while sensors with higher numbers of pixels per unit area are likely to suffer higher noise levels.
For these reasons, it is possible to obtain cheap digital cameras with sensor sizes much smaller than 35mm film, but with high pixel counts, that can still produce high-resolution images. Such cameras are usually supplied with lenses that would be classed as extremely wide angle on a 35mm camera, and that can also be smaller size and less expensive, since there is a smaller sensor to illuminate. For example, a camera with a 1/1.8" sensor has a 5.0x field of view crop, and so a hypothetical 5-50mm zoom lens produces images that look similar (again the differences mentioned above are important) to those produced by a 35mm film camera with a 25–250mm lens, while being much more compact than such a lens for a 35mm camera since the imaging circle is much smaller.
This can be useful if extra telephoto reach is desired, as a certain lens on an APS sensor produces an image equivalent to a significantly longer lens on a 35mm film camera shot at the same distance from the subject, the equivalent length of which depends on the camera's field of view crop. This is sometimes referred to as the focal length multiplier, but the focal length is a physical attribute of the lens and not the camera system itself. The disadvantage of this is that wide angle photography is made somewhat more difficult, as the smaller sensor effectively and undesirably reduces the captured field of view. Some methods of compensating for this or otherwise producing much wider digital photographs involve using a fisheye lens
and "defishing" the image in post processing to simulate a rectilinear
wide angle lens.
Full-frame digital SLRs, that is, those with sensor size matching a frame of 35mm film, include Canon 1Ds and 5D series, Kodak Pro DCS-14n, Nikon D3 line and Contax N Digital. There are very few digital cameras with sensors that can approach the resolution of larger-format film cameras, with the possible exception of the Mamiya
ZD (22MP) and the Hasselblad
H3D series of DSLRs (22 to 39 MP).
Common values for field of view crop in DSLRs include 1.3x for some Canon
(APS-H) sensors, 1.5x for Sony
APS-C sensors used by Nikon
, Pentax
and Konica Minolta
and for Fujifilm
sensors, 1.6 (APS-C) for most Canon sensors, ~1.7x for Sigma
's Foveon
sensors and 2x for Kodak and Panasonic
4/3" sensors currently used by Olympus and Panasonic
. Crop factors for non-SLR consumer compact and bridge
cameras are larger, frequently 4x or more.
A common alternative is the use of a card reader
which may be capable of reading several types of storage media, as well as high speed transfer of data to the computer. Use of a card reader also avoids draining the camera battery during the download process, as the device takes power from the USB port
. An external card reader allows convenient direct access to the images on a collection of storage media. But if only one storage card is in use, moving it back and forth between the camera and the reader can be inconvenient. Many computers have a card reader built in, at least for SD cards.
standard, which allows them to send data directly to a PictBridge-capable computer printer
without the need for a computer.
Wireless connectivity can also provide for printing photos without a cable connection.
Polaroid has introduced a printer integrated into its digital camera which creates a small, printed copy of a photo. This is reminiscent of the original instant camera
, popularized by Polaroid in 1975.
HDMI
has been adopted by many high-end digital camera makers, to show photos in their high-resolution quality on an HDTV.
In January 2008, Silicon Image announced a new technology for sending video from mobile devices to a television in digital form. MHL
sends pictures as a video stream, up to 1080p resolution, and is compatible with HDMI.
Some DVD recorders and television sets can read memory cards used in cameras; alternatively several types of flash card readers have TV output capability.
for different applications. Within the constraints of correct exposure various parameters can be changed, including exposure
, aperture
, focus
ing, light meter
ing, white balance, and equivalent sensitivity. For example a portrait
might use a wider aperture to render the background out of focus, and would seek out and focus on a human face rather than other image content.
Many camera phone
s and most separate digital cameras use memory card
s having flash memory
to store image data. The majority of cards for separate cameras are SD
format; many are CompactFlash
or other formats.
Digital cameras have computers inside, hence have internal memory, and many cameras can use some of this internal memory for a limited capacity for pictures that can be transferred to or from the card or through the camera's connections.
A few cameras use some other form of removable storage
such as Microdrive
s (very small hard disk drives), CD single
(185 MB
), and 3.5" floppy disks. Other unusual formats include:
Most manufacturers of digital cameras do not provide drivers and software to allow their cameras to work with Linux
or other free software
. Still, many cameras use the standard USB storage protocol, and are thus easily usable. Other cameras are supported by the gPhoto
project.
) is the most common file format for storing image data. Other file types include Tagged Image File Format (TIFF) and various Raw image format
s.
Many cameras, especially high-end ones, support a raw image format
. A raw image is the unprocessed set of pixel data directly from the camera's sensor, often saved in a proprietary format. Adobe Systems
has released the DNG format, a royalty-free raw image format used by at least 10 camera manufacturers.
Raw files initially had to be processed in specialized image editing
programs, but over time many mainstream editing programs, such as Google's Picasa
, have added support for raw images. Rendering to standard images from raw sensor data allows more flexibility in making major adjustments without losing image quality or retaking the picture.
Formats for movies are AVI
, DV
, MPEG, MOV (often containing motion JPEG), WMV, and ASF (basically the same as WMV). Recent formats include MP4, which is based on the QuickTime format and uses newer compression algorithms to allow longer recording times in the same space.
Other formats that are used in cameras but not for pictures are the Design Rule for Camera Format (DCF
), an ISO specification for the camera's internal file structure and naming, and Digital Print Order Format (DPOF
), which dictates what order images are to be printed in and how many copies.
Most cameras include Exif
data that provides metadata
about the picture. Exif data may include aperture
, exposure time, focal length
, date and time taken, and location.
requirements, and over time have become smaller, resulting in an ongoing need to develop a battery
small enough to fit in the camera and yet able to power it for a reasonable length of time.
Two broad types of batteries are in use for digital cameras.
or reusable rechargeable batteries. In either case they conform to an established off-the-shelf form factor, most commonly AA
, CR2, or CR-V3
batteries, with AAA batteries
in a handful of cameras. The CR2 and CR-V3 batteries are lithium based
, and intended for single use. They are also commonly seen in camcorders. AA batteries are the most common; however, the non-rechargeable alkaline batteries supplied with low-end cameras are capable of powering most cameras for only a very short time. They may serve satisfactorily in cameras that are only occasionally used.
Consumers with more than an occasional need use AA Nickel metal hydride batteries
(NiMH) instead, which provide adequate energy and are rechargeable. NIMH batteries do not provide as much energy per volume as lithium ion batteries
, and they also tend to discharge when not used. For the same energy, a NiMH rechargeable battery
takes up to twice the volume of a Li-on rechargeable battery, and is three to five times heavier, but only costs half as much. Rechargeable batteries are available in various ampere-hour
(Ah) or milli
-ampere-hour (mAh) ratings, which are approximately proportional to shots per charge.
Typically mid-range consumer models and some low end cameras use off-the-shelf batteries; only a very few DSLR
cameras accept them (for example, Sigma SD10
). Rechargeable RCR-V3 lithium-ion batteries are also available as an alternative to non-rechargeable CR-V3 batteries. Cameras, especially earlier ones made for AA-size batteries assumed that these would be of the non-rechargeable, preferably alkaline manganese type delivering 1.5 volts per cell. Rechargeable NiCd or NiMH cells only deliver 1.2 volts, which means that many such cameras will only operate for a short time or not at all even with new and newly charged 1.2 volt units. A portable ultra-high-endurance external power-supply for the shoulder bag to operate older 6 volt cameras can be made up of five 1.2 volt C-size cells which can be either NiCd or NiMH, with a cable and 4mm DC-plug.
. Almost all proprietary batteries are lithium ion
. While they only accept a certain number of recharges before the battery life begins degrading (typically up to 500 cycles), they provide considerable performance for their size. A result is that at the two ends of the spectrum both high end professional cameras and low end consumer models tend to use lithium ion batteries.
Many early professional SLR cameras, such as the Kodak DCS
series, were developed from 35 mm film cameras. The technology of the time, however, meant that rather than being digital "backs" the bodies of these cameras were mounted on large, bulky digital units, often bigger than the camera portion itself. These were factory built cameras, however, not aftermarket conversions.
A notable exception is the Nikon E2, followed by Nikon E3
, using additional optics to convert the 35mm format to a 2/3 CCD-sensor.
A few 35 mm cameras have had digital camera back
s made by their manufacturer, Leica being a notable example. Medium format and large format
cameras (those using film stock greater than 35 mm), have a low unit production, and typical digital backs for them cost over $10,000. These cameras also tend to be highly modular, with handgrips, film backs, winders, and lenses available separately to fit various needs.
The very large sensor these backs use leads to enormous image sizes. For example Phase One's P45 39 MP image back creates a single TIFF image of size up to 224.6 MB, and even greater pixel counts are available. Medium format digitals such as this are geared more towards studio and portrait photography than their smaller DSLR counterparts; the ISO speed in particular tends to have a maximum of 400, versus 6400 for some DSLR cameras. (Canon EOS-1D Mark IV and Nikon D3S
have ISO 12800 plus Hi-3 ISO 102400 with the Canon EOS-1Dx's ISO of 204800)
cameras, such as the Mamiya
645D series, allow installation of either a digital camera back or a traditional photographic film back.
Linear array cameras are also called scan backs.
Most earlier digital camera backs used linear array sensors. The linear array sensor acts like its counterpart in a flatbed image scanner
by moving vertically to digitize the image. Many early such cameras only capture grayscale
images. Color photography requires three separate scans, and a mechanical assembly to cycle a primary color filter in front of the sensor. These are called multi-shot backs. The entire scanning process requires relatively long expsoure times, in the range of seconds or even minutes. Due to this relatively long exposure-time, scanning and mutli-shot backs are generally limited to studio applications, where all aspects of the photographic scene are under the photographer's control.
Some other camera backs use CCD arrays similar to typical cameras. These are called single-shot backs.
Since it is much easier to manufacture a high-quality linear CCD array with only thousands of pixels than a CCD matrix with millions, very high resolution linear CCD camera backs were available much earlier than their CCD matrix counterparts. For example, you could buy an (albeit expensive) camera back with over 7,000 pixel horizontal resolution in the mid-1990s. However, , it is still difficult to buy a comparable CCD matrix camera of the same resolution. Rotating line cameras, with about 10,000 color pixels in its sensor line, are able, , to capture about 120,000 lines during one full 360 degree rotation, thereby creating a single digital image of 1,200 Megapixels.
Most modern digital camera backs use CCD or CMOS matrix sensors. The matrix sensor captures the entire image frame at once, instead of incrementing scanning the frame area through the prolonged exposure. For example, Phase One produces a 39 million pixel digital camera back with a 49.1 x 36.8 mm CCD in 2008. This CCD array is a little smaller than a frame of 120 film
and much larger than a 35 mm
frame (36 x 24 mm). In comparison, consumer digital cameras use arrays ranging from 36 x 24 mm (full frame on high end consumer DSLRs) to 7.2 x 5.3 mm (on point and shoot cameras) CMOS sensor.
At present, there are relatively few complete digital SLR cameras with sensors large enough to compete with the image detail offered by medium to large format film cameras. Phase One, Mamiya
, and Hasselblad
in 2011 manufacture medium format digital devices that can capture 30MP up to 80MP. The units tend to be quite large and expensive. Additionally, because of their high build quality and lack of moving parts, they tend to be quite long lasting and are prominent on the used market.
Camera
A camera is a device that records and stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images...
that takes video
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
or still photograph
Photograph
A photograph is an image created by light falling on a light-sensitive surface, usually photographic film or an electronic imager such as a CCD or a CMOS chip. Most photographs are created using a camera, which uses a lens to focus the scene's visible wavelengths of light into a reproduction of...
s, or both, digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
ly by recording images
Digital image
A digital image is a numeric representation of a two-dimensional image. Depending on whether or not the image resolution is fixed, it may be of vector or raster type...
via an electronic
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
image sensor
Image sensor
An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras and other imaging devices...
. It is the main device used in the field of digital photography
Digital photography
Digital photography is a form of photography that uses an array of light sensitive sensors to capture the image focused by the lens, as opposed to an exposure on light sensitive film...
. Most 21st century cameras are digital.
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
with sound
Sound recording and reproduction
Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording...
as well as still photograph
Photograph
A photograph is an image created by light falling on a light-sensitive surface, usually photographic film or an electronic imager such as a CCD or a CMOS chip. Most photographs are created using a camera, which uses a lens to focus the scene's visible wavelengths of light into a reproduction of...
s. Some can crop
Cropping (image)
Cropping refers to the removal of the outer parts of an image to improve framing, accentuate subject matter or change aspect ratio. Depending on the application, this may be performed on a physical photograph, artwork or film footage, or achieved digitally using image editing software...
and stitch
Image stitching
Image stitching or photo stitching is the process of combining multiple photographic images with overlapping fields of view to produce a segmented panorama or high-resolution image. Commonly performed through the use of computer software, most approaches to image stitching require nearly exact...
pictures and perform other elementary image editing
Image editing
Image editing encompasses the processes of altering images, whether they be digital photographs, traditional analog photographs, or illustrations. Traditional analog image editing is known as photo retouching, using tools such as an airbrush to modify photographs, or editing illustrations with any...
. Some have a GPS receiver built in, and can produce Geotagged photographs.
The optical system works the same as in film cameras, typically using a lens with a variable diaphragm
Diaphragm (optics)
In optics, a diaphragm is a thin opaque structure with an opening at its center. The role of the diaphragm is to stop the passage of light, except for the light passing through the aperture...
to focus light onto an image pickup device. The diaphragm and shutter admit the correct amount of light to the imager, just as with film but the image pickup device is electronic rather than chemical. Most digicams, apart from camera phones and a few specialized types, have a standard tripod screw.
Digital cameras are incorporated into many devices ranging from PDA
Personal digital assistant
A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...
s and mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s (called camera phone
Camera phone
A camera phone is a mobile phone which is able to capture still photographs . Since early in the 21st century the majority of mobile phones in use are camera phones....
s) to vehicles. The Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
and other astronomical
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
devices are essentially specialized digital cameras.
Types of digital cameras
Digital cameras are made in a wide range of sizes, prices and capabilities. The majority are camera phoneCamera phone
A camera phone is a mobile phone which is able to capture still photographs . Since early in the 21st century the majority of mobile phones in use are camera phones....
s, operated as a mobile application through the cellphone menu. Professional photographers and many amateurs use larger, more expensive digital single-lens reflex camera
Digital single-lens reflex camera
Most digital single-lens reflex cameras are digital cameras that use a mechanical mirror system and pentaprism to direct light from the lens to an optical viewfinder on the back of the camera....
s (DSLR) for their greater versatility. Between these extremes lie digital compact cameras and bridge digital camera
Bridge digital camera
Bridge cameras are cameras which fill the niche between the single-lens reflex cameras and the Point-and-shoot camera. They are often comparable in size and weight to the smallest Digital SLRs , but almost all digital bridge cameras lack an optical viewfinder system...
s that "bridge" the gap between amateur and professional cameras. Specialized cameras including multispectral imaging equipment and astrograph
Astrograph
An astrograph is a telescope designed for the sole purpose of astrophotography. Astrographs are usually used in wide field surveys of the night sky as well as detection of objects such as asteroids, meteors, and comets.-Design:...
s continue to serve the scientific, military, medical and other special purposes for which digital photography
Digital photography
Digital photography is a form of photography that uses an array of light sensitive sensors to capture the image focused by the lens, as opposed to an exposure on light sensitive film...
was invented.
Compact digital cameras
Compact cameras are designed to be tiny and portable and are particularly suitable for casual and "snapshotSnapshot
Snapshot may refer to:* Snapshot , an amateur photograph* Snapshot, a 1979 Australian film directed by Simon Wincer* Snapshot, a novel by Garry Disher...
" uses. Hence, they are also called point-and-shoot cameras. The smallest, generally less than 20 mm thick, are described as subcompacts
Subminiature photography
Subminiature photography is photography with unusually small cameras using unusually small film formats. It is distinct from photomicrography, photographing microscopic subjects with a camera which is not particularly small....
or "ultra-compacts" and some are nearly credit card size.
Most, apart from ruggedized or water-resistant models
Waterproof digital camera
Waterproof digital cameras are digital cameras that can make pictures underwater. Waterproof housings have long been made but they cost almost as the cameras...
, incorporate a retractable lens assembly allowing a thin camera to have a moderately long focal length
Focal length
The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus...
and thus fully exploit an image sensor larger than that on a camera phone, and a mechanized lens cap to cover the lens when retracted. The retracted and capped lens is protected from keys, coins and other hard objects, thus making it a thin, pocketable package. Subcompacts commonly have one lug and a short wrist strap which aids extraction from a pocket, while thicker compacts may have two lugs for attaching a neck strap.
Compact cameras are usually designed to be easy to use
Usability
Usability is the ease of use and learnability of a human-made object. The object of use can be a software application, website, book, tool, machine, process, or anything a human interacts with. A usability study may be conducted as a primary job function by a usability analyst or as a secondary job...
, sacrificing advanced features and picture quality for compactness and simplicity; images can usually only be stored using lossy compression (JPEG
JPEG
In computing, JPEG . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality....
). Most have a built-in flash
Flash (photography)
A flash is a device used in photography producing a flash of artificial light at a color temperature of about 5500 K to help illuminate a scene. A major purpose of a flash is to illuminate a dark scene. Other uses are capturing quickly moving objects or changing the quality of light...
usually of low power, sufficient for nearby subjects. Live preview
Live preview
Live preview is a feature that allows a digital camera's display screen to be used as a viewfinder. This provides a means of previewing framing and other exposure before taking the photograph. In most such cameras, the preview is generated by means of continuously and directly projecting the image...
is almost always used to frame the photo. Most have limited motion picture capability. Compacts often have macro
Macro photography
Macrophotography is close-up photography, usually of very small subjects. Classically a macrophotograph is one in which the size of the subject on the negative is greater than life size. However in modern use it refers to a finished photograph of a subject at greater than life size...
capability and zoom lens
Zoom lens
A zoom lens is a mechanical assembly of lens elements for which the focal length can be varied, as opposed to a fixed focal length lens...
es but the zoom range is usually less than for bridge
Bridge digital camera
Bridge cameras are cameras which fill the niche between the single-lens reflex cameras and the Point-and-shoot camera. They are often comparable in size and weight to the smallest Digital SLRs , but almost all digital bridge cameras lack an optical viewfinder system...
and DSLR
Digital single-lens reflex camera
Most digital single-lens reflex cameras are digital cameras that use a mechanical mirror system and pentaprism to direct light from the lens to an optical viewfinder on the back of the camera....
cameras. Generally a contrast-detect autofocus
Autofocus
An autofocus optical system uses a sensor, a control system and a motor to focus fully automatic or on a manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication...
system, using the image data from the live preview feed of the main imager, focuses the lens.
Typically, these cameras incorporate a nearly silent leaf shutter into their lenses.
For lower cost and smaller size, these cameras typically use image sensor
Image sensor
An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras and other imaging devices...
s with a diagonal of approximately 6 mm, corresponding to a crop factor
Crop factor
In digital photography, a crop factor is related to the ratio of the dimensions of a camera's imaging area compared to a reference format; most often, this term is applied to digital cameras, relative to 35 mm film format as a reference. In the case of digital cameras, the imaging device would be a...
around 6. This gives them weaker low-light performance, greater depth of field
Depth of field
In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...
, generally closer focusing ability, and smaller components than cameras using larger sensors.
Starting in 2011, some compact digital cameras can take 3D still photos. These 3D compact stereo camera
Stereo camera
A stereo camera is a type of camera with two or more lenses with a separate image sensor or film frame for each lens. This allows the camera to simulate human binocular vision, and therefore gives it the ability to capture three-dimensional images, a process known as stereo photography. Stereo...
s can capture 3D panoramic photos for play back on a 3D TV. Some of these are rugged and waterproof, and some have GPS
GeoTagging
Geotagging is the process of adding geographical identification metadata to various media such as a geotagged photograph or video, websites, SMS messages, QR Codes or RSS feeds and is a form of geospatial metadata...
, compass, barometer
Barometer
A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure tendency can forecast short term changes in the weather...
and altimeter
Altimeter
An altimeter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth underwater.-Pressure altimeter:...
.
Bridge cameras
Bridge are higher-end digital cameras that physically and ergonomically resemble DSLRs and share with them some advanced features, but share with compacts the use of a fixed lens and a small sensor. Like compacts, most use live previewLive preview
Live preview is a feature that allows a digital camera's display screen to be used as a viewfinder. This provides a means of previewing framing and other exposure before taking the photograph. In most such cameras, the preview is generated by means of continuously and directly projecting the image...
to frame the image. Their autofocus
Autofocus
An autofocus optical system uses a sensor, a control system and a motor to focus fully automatic or on a manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication...
uses the same contrast-detect mechanism, but many bridge cameras have a manual focus
Manual focus
In the field of photography, a manual focus camera is one in which the operator has to adjust the focus of the lens by hand. Before the advent of autofocus, all cameras had manually adjusted focusing; thus, the term is a retronym....
mode, in some cases using a separate focus ring, for greater control. They originally "bridged" the gap between affordable point-and-shoot cameras and the then unaffordable earlier digital SLRs.
Due to the combination of big physical size but a small sensor, many of these cameras have very highly specified lenses with large zoom range and fast aperture
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...
, partially compensating for the inability to change lenses. On some, the lens qualifies as superzoom
Superzoom
The term hyperzoom or superzoom is used to advertise photographic zoom lenses with unconventionally large focal length factors, typically more than 5× and ranging up to 15×, e.g., 35 mm to 350 mm. The largest ratio for digital SLR cameras is held by the Tamron 18–270 mm, giving 15×....
. To compensate for the lesser sensitivity of their small sensors, these cameras almost always include an image stabilization
Image stabilization
Image stabilization is a family of techniques used to reduce blurring associated with the motion of a camera during exposure. Specifically, it compensates for pan and tilt of a camera or other imaging device. It is used in image-stabilized binoculars, still and video cameras, and astronomical...
system to enable longer handheld exposures.
These cameras are sometimes marketed as and confused with digital SLR cameras since the appearance is similar. Bridge cameras lack the reflex viewing system of DSLRs, are usually fitted with fixed (non-interchangeable) lenses (although some have a lens thread to attach accessory wide-angle or telephoto converters
Teleconverter
A teleconverter is a secondary lens which is mounted between the camera and a photographic lens. Its job is to enlarge the central part of an image obtained by the objective lens...
), and can usually take movies with sound. The scene is composed by viewing either the liquid crystal display or the electronic viewfinder
Electronic viewfinder
An electronic viewfinder or EVF is a viewfinder where the image captured by the lens is projected electronically onto a miniature display. The image on this display is used to assist in aiming the camera at the scene to be photographed.-Operation:...
(EVF). Most have a longer shutter lag
Shutter lag
In photography, shutter lag is the delay between triggering the shutter and when the photograph is actually recorded. This is a common problem in the photography of fast-moving objects or people in motion...
than a true dSLR, but they are capable of good image quality (with sufficient light) while being more compact and lighter than DSLRs. High-end models of this type have comparable resolutions to low and mid-range DSLRs. Many of these cameras can store images in a Raw image format
RAW image format
A camera raw image file contains minimally processed data from the image sensor of either a digital camera, image scanner, or motion picture film scanner. Raw files are so named because they are not yet processed and therefore are not ready to be printed or edited with a bitmap graphics editor...
, or processed and JPEG
JPEG
In computing, JPEG . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality....
compressed, or both. The majority have a built-in flash similar to those found in DSLRs.
In bright sun, the quality difference between a good compact camera and a digital SLR is minimal but bridgecams are more portable, cost less and have a similar zoom ability to dSLR. Thus a Bridge camera may better suit outdoor daytime activities, except when seeking professional-quality photos.
In low light conditions and/or at ISO equivalents
Film speed
Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system....
above 800, most bridge cameras (or megazooms) lack in image quality when compared to even entry level DSLRs. However, they do have one major advantage: their much larger depth of field
Depth of field
In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...
due to the small sensor as compared to a DSLR, allowing larger apertures with shorter exposure times.
A 3D Photo Mode
Stereoscopy
Stereoscopy refers to a technique for creating or enhancing the illusion of depth in an image by presenting two offset images separately to the left and right eye of the viewer. Both of these 2-D offset images are then combined in the brain to give the perception of 3-D depth...
was introduced in 2011, whereby the camera automatically takes a second image from a slightly different perspective and provides a standard .MPO file for stereo display.
Mirrorless interchangeable-lens camera
In late 2008, a new type of camera emerged, combining the larger sensors and interchangeable lenses of DSLRs with the live-preview viewing system of compact cameras, either through an electronic viewfinderElectronic viewfinder
An electronic viewfinder or EVF is a viewfinder where the image captured by the lens is projected electronically onto a miniature display. The image on this display is used to assist in aiming the camera at the scene to be photographed.-Operation:...
or on the rear LCD. These are simpler and more compact than DSLRs due to the removal of the mirror box, and typically emulate the handling and ergonomics of either DSLRs or compacts. The system is used by Micro Four Thirds, borrowing components from the Four Thirds DSLR system.
Digital single lens reflex cameras
Digital single-lens reflex cameras (DSLRs) are digital cameras based on film single-lens reflex cameraSingle-lens reflex camera
A single-lens reflex camera is a camera that typically uses a semi-automatic moving mirror system that permits the photographer to see exactly what will be captured by the film or digital imaging system, as opposed to pre-SLR cameras where the view through the viewfinder could be significantly...
s (SLRs). They take their name from their unique viewing system, in which a mirror reflects light from the lens through a separate optical viewfinder. At the moment of exposure the mirror flips out of the way, making a distinctive "clack" sound and allowing light to fall on the imager.
Since no light reaches the imager during framing, autofocus
Autofocus
An autofocus optical system uses a sensor, a control system and a motor to focus fully automatic or on a manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication...
is accomplished using specialized sensors in the mirror box itself. Most 21st century DSLRs also have a "live view" mode that emulates the live preview system of compact cameras, when selected.
These cameras have much larger sensors than the other types, typically 18 mm to 36 mm on the diagonal (crop factor
Crop factor
In digital photography, a crop factor is related to the ratio of the dimensions of a camera's imaging area compared to a reference format; most often, this term is applied to digital cameras, relative to 35 mm film format as a reference. In the case of digital cameras, the imaging device would be a...
2, 1.6, or 1). This gives them superior low-light performance, less depth of field
Depth of field
In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...
at a given aperture, and a larger size.
They make use of interchangeable lenses; each major DSLR manufacturer also sells a line of lenses specifically intended to be used on their cameras. This allows the user to select a lens designed for the application at hand: wide-angle, telephoto, low-light, etc. So each lens does not require its own shutter, DSLRs use a focal-plane shutter
Focal-plane shutter
In camera design, a focal-plane shutter is a type of photographic shutter that is positioned immediately in front of the focal plane of the camera, that is, right in front of the photographic film or image sensor.-Two-curtain shutters:...
in front of the imager, behind the mirror.
Digital rangefinders
A rangefinder is a user-operated optical mechanism to measure subject distance once widely used on film cameras. Most digital cameras measure subject distance automatically using electro-optical techniques, but it is not customary to say that they have a rangefinder.Line-scan camera systems
A line-scan camera is a camera device containing a line-scan image sensorImage sensor
An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras and other imaging devices...
chip, and a focusing mechanism. These cameras are almost solely used in industrial settings to capture an image of a constant stream of moving material. Unlike video cameras, line-scan cameras use a single row of pixel sensors
Active pixel sensor
An active-pixel sensor is an image sensor consisting of an integrated circuit containing an array of pixel sensors, each pixel containing a photodetector and an active amplifier. There are many types of active pixel sensors including the CMOS APS used most commonly in cell phone cameras, web...
, instead of a matrix of them. Data coming from the line-scan camera has a frequency, where the camera scans a line, waits, and repeats. The data coming from the line-scan camera is commonly processed by a computer, to collect the one-dimensional line data and to create a two-dimensional image. The collected two-dimensional image data is then processed by image-processing methods for industrial purposes.
Integration
Many devices include digital cameras built into or integrated into them. For example, mobile phones often include digital cameras; those that do are known as camera phoneCamera phone
A camera phone is a mobile phone which is able to capture still photographs . Since early in the 21st century the majority of mobile phones in use are camera phones....
s. Other small electronic devices (especially those used for communication) such as PDA
Personal digital assistant
A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...
s, laptops and BlackBerry
BlackBerry
BlackBerry is a line of mobile email and smartphone devices developed and designed by Canadian company Research In Motion since 1999.BlackBerry devices are smartphones, designed to function as personal digital assistants, portable media players, internet browsers, gaming devices, and much more...
devices often contain an integral digital camera, and most 21st century camcorder
Camcorder
A camcorder is an electronic device that combines a video camera and a video recorder into one unit. Equipment manufacturers do not seem to have strict guidelines for the term usage...
s can also make still pictures.
Due to the limited storage capacity and general emphasis on convenience rather than image quality, almost all these integrated or converged devices store images in the lossy but compact JPEG
JPEG
In computing, JPEG . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality....
file format.
Mobile phones incorporating digital cameras were introduced in Japan in 2001 by J-Phone. In 2003 camera phones outsold stand-alone digital cameras, and in 2006 they outsold all film-based cameras and digital cameras combined. These camera phones reached a billion devices sold in only five years, and by 2007 more than half of the installed base
Installed base
Installed base or installed user base is a measure of the number of units of a particular type of system—usually a computing platform—actually in use, as opposed to market share, which only reflects sales over a particular period. Because installed base includes machines that may have been in use...
of all mobile phones were camera phones. Sales of separate cameras peaked in 2008.
Integrated cameras tend to be at the very lowest end of the scale of digital cameras in technical specifications, such as resolution, optical quality, and ability to use accessories. With rapid development, however, the gap between mainstream compact digital cameras and camera phones is closing, and high-end camera phones are competitive with low-end stand-alone digital cameras of the same generation.
History
Steven SassonSteven Sasson
Steven J. Sasson , is an American electrical engineer and the inventor of the digital camera. Sasson is a 1972 and 1973 graduate of Rensselaer Polytechnic Institute in electrical engineering.-Biography:...
as an engineer at Eastman Kodak
Eastman Kodak
Eastman Kodak Company is a multinational imaging and photographic equipment, materials and services company headquarted in Rochester, New York, United States. It was founded by George Eastman in 1892....
invented and built the first digital camera using a charge-coupled device
Charge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
image sensor in 1975.
Image resolution
The resolutionImage resolution
Image resolution is an umbrella term that describes the detail an image holds. The term applies to raster digital images, film images, and other types of images. Higher resolution means more image detail....
of a digital camera is often limited by the image sensor
Image sensor
An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras and other imaging devices...
(typically a CCD
Charge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
or CMOS sensor chip) that turns light into discrete signals, replacing the job of film in traditional photography.
The sensor is made up of millions of "buckets" that essentially count the number of photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s that strike the sensor.
This means that the brighter the image at a given point on the sensor, the larger the value that is read for that pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
.
Depending on the physical structure of the sensor, a color filter array
Color filter array
In photography, a color filter array , or color filter mosaic , is a mosaic of tiny color filters placed over the pixel sensors of an image sensor to capture color information....
may be used which requires a demosaicing
Demosaicing
A demosaicing algorithm is a digital image process used to reconstruct a full color image from the incomplete color samples output from an image sensor overlaid with a color filter array...
/interpolation algorithm.
The number of resulting pixels in the image determines its "pixel count".
For example, a 640x480 image would have 307,200 pixels, or approximately 307 kilopixels; a 3872x2592 image would have 10,036,224 pixels, or approximately 10 megapixels.
The pixel count alone is commonly presumed to indicate the resolution of a camera, but this simple figure of merit
Figure of merit
A figure of merit is a quantity used to characterize the performance of a device, system or method, relative to its alternatives. In engineering, figures of merit are often defined for particular materials or devices in order to determine their relative utility for an application...
is a misconception. Other factors impact a sensor's resolution, including sensor size, lens quality, and the organization of the pixels (for example, a monochrome camera without a Bayer filter
Bayer filter
A Bayer filter mosaic is a color filter array for arranging RGB color filters on a square grid of photosensors. Its particular arrangement of color filters is used in most single-chip digital image sensors used in digital cameras, camcorders, and scanners to create a color image...
mosaic has a higher resolution than a typical color camera).
Where such other factors limit the resolution, a greater pixel count does not improve it, but may rather make the digital images inconveniently large and/or exacerbate image noise
Image noise
Image noise is random variation of brightness or color information in images, and is usually an aspect of electronic noise. It can be produced by the sensor and circuitry of a scanner or digital camera...
. Many digital compact cameras are criticized for having excessive pixels. Sensors can be so small that their 'buckets' can easily overfill; again, resolution of a sensor can become greater than the camera lens could possibly deliver.
Demanding high quality and resolution (e.g. for use in professional photography), this count is an object of manufacturer competition. As of August 2011, the highest resolution available on the market is 80.1 MP.
Moore's Law
Moore's law describes a long-term trend in the history of computing hardware: the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years....
. This predictability of camera prices was first presented in 1998 at the Australian PMA DIMA conference by Barry Hendy and since referred to as "Hendy's Law".
Since only a few aspect ratio
Aspect ratio (image)
The aspect ratio of an image is the ratio of the width of the image to its height, expressed as two numbers separated by a colon. That is, for an x:y aspect ratio, no matter how big or small the image is, if the width is divided into x units of equal length and the height is measured using this...
s are commonly used (mainly 4:3 and 3:2), the number of sensor sizes that are useful is limited. Furthermore, sensor manufacturers do not produce every possible sensor size, but take incremental steps in sizes. For example, in 2007 the three largest sensors (in terms of pixel count) used by Canon were the 21.1, 17.9, and 16.6 megapixel CMOS sensors.
Methods of image capture
The first method is often called single-shot, in reference to the number of times the camera's sensor is exposed to the light passing through the camera lens. Single-shot capture systems use either one CCD with a Bayer filter
Bayer filter
A Bayer filter mosaic is a color filter array for arranging RGB color filters on a square grid of photosensors. Its particular arrangement of color filters is used in most single-chip digital image sensors used in digital cameras, camcorders, and scanners to create a color image...
mosaic, or three separate image sensor
Image sensor
An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras and other imaging devices...
s (one each for the primary additive colors red, green, and blue) which are exposed to the same image via a beam splitter.
The second method is referred to as multi-shot because the sensor is exposed to the image in a sequence of three or more openings of the lens aperture. There are several methods of application of the multi-shot technique. The most common originally was to use a single image sensor
Image sensor
An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras and other imaging devices...
with three filters (once again red, green and blue) passed in front of the sensor in sequence to obtain the additive color information. Another multiple shot method is called Microscanning
Microscanning
Microscanning is a method for increasing resolution of digital cameras. With the color co-site sampling identically colored pixels in several frames of the specimen, obtained by moving the sensor with a piezo mechanism in a regular raster, are combined to a sharp resulting image...
. This technique utilizes a single CCD with a Bayer filter but actually moved the physical location of the sensor chip on the focus plane of the lens to "stitch" together a higher resolution image than the CCD would allow otherwise. A third version combined the two methods without a Bayer filter on the chip.
The third method is called scanning because the sensor moves across the focal plane much like the sensor of a desktop scanner. Their linear or tri-linear sensors utilize only a single line of photosensors, or three lines for the three colors. In some cases, scanning is accomplished by moving the sensor e.g. when using Color co-site sampling
Color co-site sampling
Color co-site sampling is a system of photographic color sensing, wherein 4, 16 or 36 images are collected from the sensor and merged to form a single image. Each subsequent image physically moves the sensor by exactly one pixel, in order to collect R, G and B data for each pixel, known as...
or rotate the whole camera; a digital rotating line camera
Rotating line camera
A rotating line camera, is a digital camera that uses a linear CCD array to assemble a digital image as the camera rotates. The CCD array may consist of three sensor lines, one for each RGB color channel...
offers images of very high total resolution.
The choice of method for a given capture is determined largely by the subject matter. It is usually inappropriate to attempt to capture a subject that moves with anything but a single-shot system. However, the higher color fidelity and larger file sizes and resolutions available with multi-shot and scanning backs make them attractive for commercial photographers working with stationary subjects and large-format photographs.
Dramatic improvements in single-shot cameras and raw image file
RAW image format
A camera raw image file contains minimally processed data from the image sensor of either a digital camera, image scanner, or motion picture film scanner. Raw files are so named because they are not yet processed and therefore are not ready to be printed or edited with a bitmap graphics editor...
processing at the beginning of the 21st century made single shot, CCD-based cameras almost completely dominant, even in high-end commercial photography. CMOS-based single shot cameras remained somewhat common.
Filter mosaics, interpolation, and aliasing
Bayer filter
A Bayer filter mosaic is a color filter array for arranging RGB color filters on a square grid of photosensors. Its particular arrangement of color filters is used in most single-chip digital image sensors used in digital cameras, camcorders, and scanners to create a color image...
mosaic in combination with an optical anti-aliasing filter
Anti-aliasing filter
An anti-aliasing filter is a filter used before a signal sampler, to restrict the bandwidth of a signal to approximately satisfy the sampling theorem....
to reduce the aliasing due to the reduced sampling of the different primary-color images.
A demosaicing
Demosaicing
A demosaicing algorithm is a digital image process used to reconstruct a full color image from the incomplete color samples output from an image sensor overlaid with a color filter array...
algorithm is used to interpolate
Interpolation
In the mathematical field of numerical analysis, interpolation is a method of constructing new data points within the range of a discrete set of known data points....
color information to create a full array of RGB image data.
Cameras that use a beam-splitter single-shot 3CCD
3CCD
A three-CCD camera is a camera whose imaging system uses three separate charge-coupled devices , each one taking a separate measurement of the primary colors, red, green, or blue light. Light coming into the lens is split by a trichroic prism assembly, which directs the appropriate wavelength...
approach, three-filter multi-shot approach, Color co-site sampling
Color co-site sampling
Color co-site sampling is a system of photographic color sensing, wherein 4, 16 or 36 images are collected from the sensor and merged to form a single image. Each subsequent image physically moves the sensor by exactly one pixel, in order to collect R, G and B data for each pixel, known as...
or Foveon X3 sensor
Foveon X3 sensor
The Foveon X3 sensor is a CMOSimage sensor for digital cameras, designed by Foveon, Inc. and manufactured by National Semiconductorand Dongbu Electronics....
do not use anti-aliasing filter
Anti-aliasing filter
An anti-aliasing filter is a filter used before a signal sampler, to restrict the bandwidth of a signal to approximately satisfy the sampling theorem....
s, nor demosaicing.
Firmware
Firmware
In electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...
in the camera, or a software in a raw converter program such as Adobe Camera Raw, interprets the raw data from the sensor to obtain a full color image, because the RGB color model
RGB color model
The RGB color model is an additive color model in which red, green, and blue light is added together in various ways to reproduce a broad array of colors...
requires three intensity values for each pixel: one each for the red, green, and blue (other color models, when used, also require three or more values per pixel).
A single sensor element cannot simultaneously record these three intensities, and so a color filter array
Color filter array
In photography, a color filter array , or color filter mosaic , is a mosaic of tiny color filters placed over the pixel sensors of an image sensor to capture color information....
(CFA) must be used to selectively filter a particular color for each pixel.
The Bayer filter pattern is a repeating 2×2 mosaic pattern of light filters, with green ones at opposite corners and red and blue in the other two positions. The high proportion of green takes advantage of properties of the human visual system, which determines brightness mostly from green and is far more sensitive to brightness than to hue or saturation. Sometimes a 4-color filter pattern is used, often involving two different hues of green. This provides potentially more accurate color, but requires a slightly more complicated interpolation process.
The color intensity values not captured for each pixel can be interpolated (or guessed) from the values of adjacent pixels which represent the color being calculated.
Sensor size and angle of view
Cameras with digital image sensorImage sensor
An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras and other imaging devices...
s that are smaller than the typical 35mm film size has a smaller field or angle of view
Angle of view
In photography, angle of view describes the angular extent of a given scene that is imaged by a camera. It is used interchangeably with the more general term field of view....
when used with a lens of the same focal length
Focal length
The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus...
. This is because angle of view is a function of both focal length and the sensor or film size used.
Crop factor
In digital photography, a crop factor is related to the ratio of the dimensions of a camera's imaging area compared to a reference format; most often, this term is applied to digital cameras, relative to 35 mm film format as a reference. In the case of digital cameras, the imaging device would be a...
, a factor by which a longer focal length lens would be needed to get the same field of view on a full-frame camera.
The result is geometrically similar to taking the image from the film camera and cutting it down (cropping) to the size of the sensor, ignoring various questions such as resolution. For moderately large DSLRs the crop factor may be in the range of 1.3-2 while smaller cameras use smaller sensors with a larger crop factor.
If the digital sensor has a higher or lower density of pixels per unit area than the film equivalent, then the amount of information captured differs correspondingly. While resolution can be estimated in pixels per unit area, the comparison is complex since most types of digital sensor record only a single colour at each pixel location, and different types of film have different effective resolutions. There are various trade-offs involved, since larger sensors are more expensive to manufacture and require larger lenses, while sensors with higher numbers of pixels per unit area are likely to suffer higher noise levels.
For these reasons, it is possible to obtain cheap digital cameras with sensor sizes much smaller than 35mm film, but with high pixel counts, that can still produce high-resolution images. Such cameras are usually supplied with lenses that would be classed as extremely wide angle on a 35mm camera, and that can also be smaller size and less expensive, since there is a smaller sensor to illuminate. For example, a camera with a 1/1.8" sensor has a 5.0x field of view crop, and so a hypothetical 5-50mm zoom lens produces images that look similar (again the differences mentioned above are important) to those produced by a 35mm film camera with a 25–250mm lens, while being much more compact than such a lens for a 35mm camera since the imaging circle is much smaller.
This can be useful if extra telephoto reach is desired, as a certain lens on an APS sensor produces an image equivalent to a significantly longer lens on a 35mm film camera shot at the same distance from the subject, the equivalent length of which depends on the camera's field of view crop. This is sometimes referred to as the focal length multiplier, but the focal length is a physical attribute of the lens and not the camera system itself. The disadvantage of this is that wide angle photography is made somewhat more difficult, as the smaller sensor effectively and undesirably reduces the captured field of view. Some methods of compensating for this or otherwise producing much wider digital photographs involve using a fisheye lens
Fisheye lens
In photography, a fisheye lens is a wide-angle lens that takes in a broad, panoramic and hemispherical image. Originally developed for use in meteorology to study cloud formation and called "whole-sky lenses", fisheye lenses quickly became popular in general photography for their unique, distorted...
and "defishing" the image in post processing to simulate a rectilinear
Rectilinear lens
In photography, a rectilinear lens is a photographic lens that yields images where straight features, such as the walls of buildings, appear with straight lines, as opposed to being curved. In other words, it is a lens with little or no barrel or pincushion distortion...
wide angle lens.
Full-frame digital SLRs, that is, those with sensor size matching a frame of 35mm film, include Canon 1Ds and 5D series, Kodak Pro DCS-14n, Nikon D3 line and Contax N Digital. There are very few digital cameras with sensors that can approach the resolution of larger-format film cameras, with the possible exception of the Mamiya
Mamiya
is a Japanese company that today manufactures high-end cameras and other related photographic and optical equipment. With headquarters in Tokyo, it has two manufacturing plants and a workforce of over 200 people...
ZD (22MP) and the Hasselblad
Hasselblad
Victor Hasselblad AB is a Swedish manufacturer of medium-format cameras and photographic equipment based in Gothenburg, Sweden.The company is best known for the medium-format cameras it has produced since World War II....
H3D series of DSLRs (22 to 39 MP).
Common values for field of view crop in DSLRs include 1.3x for some Canon
Canon Inc.
is a Japanese multinational corporation that specialises in the manufacture of imaging and optical products, including cameras, camcorders, photocopiers, steppers and computer printers. Its headquarters are located in Ōta, Tokyo, Japan.-Origins:...
(APS-H) sensors, 1.5x for Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
APS-C sensors used by Nikon
Nikon
, also known as just Nikon, is a multinational corporation headquartered in Tokyo, Japan, specializing in optics and imaging. Its products include cameras, binoculars, microscopes, measurement instruments, and the steppers used in the photolithography steps of semiconductor fabrication, of which...
, Pentax
Pentax
Pentax is a brand name used by Hoya Corporation for its medical-related products & services and Pentax Ricoh Imaging Company for cameras, sport optics , etc. Hoya purchased and merged with the Japanese optics company on March 31, 2008. Hoya's Pentax imaging business was sold to Ricoh Company, Ltd...
and Konica Minolta
Konica Minolta
is a Japanese manufacturer of office equipment, medical imaging, graphic imaging, optical devices, and measuring instruments. It is headquartered in the Marunouchi Center Building in Marunouchi, Chiyoda, Tokyo, with a Kansai office in Nishi-ku, Osaka, Osaka Prefecture...
and for Fujifilm
Fujifilm
is a multinational photography and imaging company headquartered in Tokyo, Japan.Fujifilm's principal activities are the development, production, sale and servicing of color photographic film, digital cameras, photofinishing equipment, color paper, photofinishing chemicals, medical imaging...
sensors, 1.6 (APS-C) for most Canon sensors, ~1.7x for Sigma
Sigma Corporation
is a Japanese company founded in 1961, manufacturing cameras, lenses, flashes and other photographic accessories. All Sigma products are produced in the company's own Aizu factory in Bandai, Fukushima, Japan...
's Foveon
Foveon
Foveon, Inc., is the company that makes the Foveon X3 sensor, which captures images in digital single-lens reflex cameras such as the Sigma Corporation SD9, SD10, SD14 and SD15 as well as in the compacts DP1, DP2 and Polaroid X530....
sensors and 2x for Kodak and Panasonic
Panasonic
Panasonic is an international brand name for Japanese electric products manufacturer Panasonic Corporation, which was formerly known as Matsushita Electric Industrial Co., Ltd...
4/3" sensors currently used by Olympus and Panasonic
Panasonic
Panasonic is an international brand name for Japanese electric products manufacturer Panasonic Corporation, which was formerly known as Matsushita Electric Industrial Co., Ltd...
. Crop factors for non-SLR consumer compact and bridge
Bridge digital camera
Bridge cameras are cameras which fill the niche between the single-lens reflex cameras and the Point-and-shoot camera. They are often comparable in size and weight to the smallest Digital SLRs , but almost all digital bridge cameras lack an optical viewfinder system...
cameras are larger, frequently 4x or more.
| Table of sensor sizes | |||
|---|---|---|---|
| Type | Width (mm) | Height (mm) | Size (mm²) |
| 1/3.6" | 4.00 | 3.00 | 12.0 |
| 1/3.2" | 4.54 | 3.42 | 15.5 |
| 1/3" | 4.80 | 3.60 | 17.3 |
| 1/2.7" | 5.37 | 4.04 | 21.7 |
| 1/2.5" | 5.76 | 4.29 | 24.7 |
| 1/2.3" | 6.16 | 4.62 | 28.5 |
| 1/2" | 6.40 | 4.80 | 30.7 |
| 1/1.8" | 7.18 | 5.32 | 38.2 |
| 1/1.7" | 7.60 | 5.70 | 43.3 |
| 2/3" | 8.80 | 6.60 | 58.1 |
| 1" | 12.8 | 9.6 | 123 |
| 4/3" Four Thirds System The Four Thirds system is a standard created by Olympus and Kodak for digital single-lens reflex camera design and development.The system provides a standard that, with digital cameras and lenses available from multiple manufacturers, allows for the interchange of lenses and bodies from different... |
18.0 | 13.5 | 243 |
| APS-C APS-C Advanced Photo System type-C is an image sensor format approximately equivalent in size to the Advanced Photo System "classic" size negatives... |
25.1 | 16.7 | 419 |
| 35 mm 135 film The term 135 was introduced by Kodak in 1934 as a designation for cartridge film wide, specifically for still photography. It quickly grew in popularity, surpassing 120 film by the late 1960s to become the most popular photographic film format... |
36 | 24 | 864 |
| Back | 48 | 36 | 1728 |
Transferring photos
Many digital cameras can connect directly to a computer to transfer data:- Early cameras used the PCPersonal computerA personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
serial portSerial portIn computing, a serial port is a serial communication physical interface through which information transfers in or out one bit at a time...
. USB is now the most widely used method (most cameras are viewable as USB mass storage), though some have a FireWireIEEE 1394 interfaceThe IEEE 1394 interface is a serial bus interface standard for high-speed communications and isochronous real-time data transfer, frequently used by personal computers, as well as in digital audio, digital video, automotive, and aeronautics applications. The interface is also known by the brand...
port. Some cameras use USB PTPPicture Transfer ProtocolPicture Transfer Protocol is a widely supported protocol developed by the International Imaging Industry Association to allow the transfer of images from digital cameras to computers and other peripheral devices without the need of additional device drivers...
mode for connection instead of USB MSC; some offer both modes. - Other cameras use wireless connections, via BluetoothBluetoothBluetooth is a proprietary open wireless technology standard for exchanging data over short distances from fixed and mobile devices, creating personal area networks with high levels of security...
or IEEE 802.11IEEE 802.11IEEE 802.11 is a set of standards for implementing wireless local area network computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee . The base version of the standard IEEE 802.11-2007 has had subsequent...
Wi-FiWi-FiWi-Fi or Wifi, is a mechanism for wirelessly connecting electronic devices. A device enabled with Wi-Fi, such as a personal computer, video game console, smartphone, or digital audio player, can connect to the Internet via a wireless network access point. An access point has a range of about 20...
, such as the Kodak EasyShare One. - Cameraphones and some high-end stand-alone digital cameras also use cellular networkCellular networkA cellular network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver known as a cell site or base station. When joined together these cells provide radio coverage over a wide geographic area...
s to connect for sharing images. The most common standard on cellular networks is the MMS Multimedia Messaging ServiceMultimedia Messaging ServiceMultimedia Messaging Service, or MMS, is a standard way to send messages that include multimedia content to and from mobile phones. It extends the core SMS capability that allowed exchange of text messages only up to 160 characters in length.The most popular use is to send photographs from...
, commonly called "picture messaging". The second method with smartphoneSmartphoneA smartphone is a high-end mobile phone built on a mobile computing platform, with more advanced computing ability and connectivity than a contemporary feature phone. The first smartphones were devices that mainly combined the functions of a personal digital assistant and a mobile phone or camera...
s is to send a picture as an email attachment. Many cameraphones do not support email, so this is less common.
A common alternative is the use of a card reader
Card reader
A card reader is a data input device that reads data from a card-shaped storage medium. Historically, paper or cardboard punched cards were used throughout the first several decades of the computer industry to store information and programs for computer system, and were read by punched card readers...
which may be capable of reading several types of storage media, as well as high speed transfer of data to the computer. Use of a card reader also avoids draining the camera battery during the download process, as the device takes power from the USB port
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
. An external card reader allows convenient direct access to the images on a collection of storage media. But if only one storage card is in use, moving it back and forth between the camera and the reader can be inconvenient. Many computers have a card reader built in, at least for SD cards.
Printing photos
Many modern cameras support the PictBridgePictBridge
PictBridge is an industry standard introduced in 2003 from the Camera & Imaging Products Association for direct printing. It allows images to be printed directly from digital cameras to a printer, without having to connect the camera to a computer. Its formal name is . CIPA DC-001-2003 Rev...
standard, which allows them to send data directly to a PictBridge-capable computer printer
Computer printer
In computing, a printer is a peripheral which produces a text or graphics of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most new printers, a...
without the need for a computer.
Wireless connectivity can also provide for printing photos without a cable connection.
Polaroid has introduced a printer integrated into its digital camera which creates a small, printed copy of a photo. This is reminiscent of the original instant camera
Instant camera
The instant camera is a type of camera that generates a developed film image. The most popular types to use self-developing film were formerly made by Polaroid Corporation....
, popularized by Polaroid in 1975.
Displaying photos
Many digital cameras include a video output port. Usually sVideo, it sends a standard-definition video signal to a television, allowing the user to show one picture at a time. Buttons or menus on the camera allow the user to select the photo, advance from one to another, or automatically send a "slide show" to the TV.HDMI
HDMI
HDMI is a compact audio/video interface for transmitting uncompressed digital data. It is a digital alternative to consumer analog standards, such as radio frequency coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA...
has been adopted by many high-end digital camera makers, to show photos in their high-resolution quality on an HDTV.
In January 2008, Silicon Image announced a new technology for sending video from mobile devices to a television in digital form. MHL
Mobile High-definition Link
Mobile High-Definition Link is a proposed industry standard for a mobile audio/video interface for directly connecting mobile phones and other portable consumer electronics devices to high-definition televisions and displays...
sends pictures as a video stream, up to 1080p resolution, and is compatible with HDMI.
Some DVD recorders and television sets can read memory cards used in cameras; alternatively several types of flash card readers have TV output capability.
Modes
Many digital cameras have preset modesMode dial
A mode dial or camera dial is a dial used on digital cameras to change the camera's mode. Most digital cameras, including dSLR and SLR-like cameras, support modes, selectable either by a dial or from a menu. On point-and-shoot cameras which support modes a range of scene types is offered. On dSLR...
for different applications. Within the constraints of correct exposure various parameters can be changed, including exposure
Exposure (photography)
In photography, exposure is the total amount of light allowed to fall on the photographic medium during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value and scene luminance over a specified area.In photographic jargon, an exposure...
, aperture
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...
, focus
Focus (optics)
In geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by...
ing, light meter
Light meter
A light meter is a device used to measure the amount of light. In photography, a light meter is often used to determine the proper exposure for a photograph...
ing, white balance, and equivalent sensitivity. For example a portrait
Portrait
thumb|250px|right|Portrait of [[Thomas Jefferson]] by [[Rembrandt Peale]], 1805. [[New-York Historical Society]].A portrait is a painting, photograph, sculpture, or other artistic representation of a person, in which the face and its expression is predominant. The intent is to display the likeness,...
might use a wider aperture to render the background out of focus, and would seek out and focus on a human face rather than other image content.
Image data storage
Camera phone
A camera phone is a mobile phone which is able to capture still photographs . Since early in the 21st century the majority of mobile phones in use are camera phones....
s and most separate digital cameras use memory card
Memory card
A memory card or flash card is an electronic flash memory data storage device used for storing digital information. They are commonly used in many electronic devices, including digital cameras, mobile phones, laptop computers, MP3 players, and video game consoles...
s having flash memory
Flash memory
Flash memory is a non-volatile computer storage chip that can be electrically erased and reprogrammed. It was developed from EEPROM and must be erased in fairly large blocks before these can be rewritten with new data...
to store image data. The majority of cards for separate cameras are SD
Secure Digital card
Secure Digital is a non-volatile memory card format developed by the SD Card Association for use in portable devices. The SD technology is used by more than 400 brands across dozens of product categories and more than 8,000 models, and is considered the de-facto industry standard.Secure Digital...
format; many are CompactFlash
CompactFlash
CompactFlash is a mass storage device format used in portable electronic devices. Most CompactFlash devices contain flash memory in a standardized enclosure. The format was first specified and produced by SanDisk in 1994...
or other formats.
Digital cameras have computers inside, hence have internal memory, and many cameras can use some of this internal memory for a limited capacity for pictures that can be transferred to or from the card or through the camera's connections.
A few cameras use some other form of removable storage
Computer storage
Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....
such as Microdrive
Microdrive
Microdrive is a brand name for a miniature, 1-inch hard disk designed to fit in a CompactFlash Type II slot. The release of similar drives by other makers has led to them often being referred to as 'microdrives'...
s (very small hard disk drives), CD single
CD single
A CD single is a music single in the form of a standard size Compact Disc, not to be confused with the 3-inch CD single, which uses a smaller form factor. The format was introduced in the mid-1980s, but did not gain its place in the market until the early 1990s...
(185 MB
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
), and 3.5" floppy disks. Other unusual formats include:
- Onboard flash memoryFlash memoryFlash memory is a non-volatile computer storage chip that can be electrically erased and reprogrammed. It was developed from EEPROM and must be erased in fairly large blocks before these can be rewritten with new data...
— Cheap cameras and cameras secondary to the device's main use (such as a camera phone) - PC CardPC CardIn computing, PC Card is the form factor of a peripheral interface designed for laptop computers. The PC Card standard was defined and developed by the Personal Computer Memory Card International Association which itself was created by a number of computer industry companies in the United States...
hard drives — early professional cameras (discontinued) - Thermal printerThermal printerA thermal printer produces a printed image by selectively heating coated thermochromic paper, or thermal paper as it is commonly known, when the paper passes over the thermal print head. The coating turns black in the areas where it is heated, producing an image...
— known only in one model of camera that printed images immediately rather than storing
Most manufacturers of digital cameras do not provide drivers and software to allow their cameras to work with Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
or other free software
Free software
Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
. Still, many cameras use the standard USB storage protocol, and are thus easily usable. Other cameras are supported by the gPhoto
GPhoto
gPhoto is a set of software applications and libraries for use in digital photography. gPhoto supports not just retrieving of images from camera devices, but also upload and remote controlled configuration and capture, depending on whether the camera supports those features.Released under the GNU...
project.
File formats
The Joint Photography Experts Group standard (JPEGJPEG
In computing, JPEG . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality....
) is the most common file format for storing image data. Other file types include Tagged Image File Format (TIFF) and various Raw image format
RAW image format
A camera raw image file contains minimally processed data from the image sensor of either a digital camera, image scanner, or motion picture film scanner. Raw files are so named because they are not yet processed and therefore are not ready to be printed or edited with a bitmap graphics editor...
s.
Many cameras, especially high-end ones, support a raw image format
RAW image format
A camera raw image file contains minimally processed data from the image sensor of either a digital camera, image scanner, or motion picture film scanner. Raw files are so named because they are not yet processed and therefore are not ready to be printed or edited with a bitmap graphics editor...
. A raw image is the unprocessed set of pixel data directly from the camera's sensor, often saved in a proprietary format. Adobe Systems
Adobe Systems
Adobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...
has released the DNG format, a royalty-free raw image format used by at least 10 camera manufacturers.
Raw files initially had to be processed in specialized image editing
Image editing
Image editing encompasses the processes of altering images, whether they be digital photographs, traditional analog photographs, or illustrations. Traditional analog image editing is known as photo retouching, using tools such as an airbrush to modify photographs, or editing illustrations with any...
programs, but over time many mainstream editing programs, such as Google's Picasa
Picasa
Picasa is an image organizer and image viewer for organizing and editing digital photos, plus an integrated photo-sharing website, originally created by Idealab in 2002 and owned by Google since 2004. "Picasa" is a blend of the name of Spanish painter Pablo Picasso, the phrase mi casa for "my...
, have added support for raw images. Rendering to standard images from raw sensor data allows more flexibility in making major adjustments without losing image quality or retaking the picture.
Formats for movies are AVI
Audio Video Interleave
Audio Video Interleave , known by its acronym AVI, is a multimedia container format introduced by Microsoft in November 1992 as part of its Video for Windows technology. AVI files can contain both audio and video data in a file container that allows synchronous audio-with-video playback...
, DV
DV
DV is a format for the digital recording and playing back of digital video. The DV codec was launched in 1995 with joint efforts of leading producers of video camcorders....
, MPEG, MOV (often containing motion JPEG), WMV, and ASF (basically the same as WMV). Recent formats include MP4, which is based on the QuickTime format and uses newer compression algorithms to allow longer recording times in the same space.
Other formats that are used in cameras but not for pictures are the Design Rule for Camera Format (DCF
Design rule for Camera File system
Design rule for Camera File system is a JEITA specification which defines a file system for digital cameras, including the directory structure, file naming method, character set, file format, and metadata format. It is currently the de facto industry standard for digital still cameras...
), an ISO specification for the camera's internal file structure and naming, and Digital Print Order Format (DPOF
DPOF
DPOF is a format which allows the user of a digital camera or other device such as a mobile phone or PDA to define which captured images on the storage card are to be printed, together with information on the number of copies or other image information such as paper size, image title text, image...
), which dictates what order images are to be printed in and how many copies.
Most cameras include Exif
Exchangeable image file format
Exchangeable image file format is a standard that specifies the formats for images, sound, and ancillary tags used by digital cameras , scanners and other systems handling image and sound files recorded by digital cameras...
data that provides metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
about the picture. Exif data may include aperture
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...
, exposure time, focal length
Focal length
The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus...
, date and time taken, and location.
Batteries
Digital cameras have high powerElectric power
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...
requirements, and over time have become smaller, resulting in an ongoing need to develop a battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
small enough to fit in the camera and yet able to power it for a reasonable length of time.
Two broad types of batteries are in use for digital cameras.
Off-the-shelf
Off-the-shelf batteries may be single-use disposablePrimary cell
A primary cell is any kind of battery in which the electrochemical reaction is not reversible, rendering the cell non-rechargeable. A common example of a primary cell is the disposable battery. Unlike a secondary cell, the reaction cannot be reversed by running a current into the cell; the chemical...
or reusable rechargeable batteries. In either case they conform to an established off-the-shelf form factor, most commonly AA
AA battery
An AA battery is a standard size of battery. Batteries of this size are the most commonly used type of in portable electronic devices. An AA battery is composed of a single electrochemical cell...
, CR2, or CR-V3
CR-V3
A CR-V3 battery is a type of disposable high-capacity 3-Volt battery used in various electronic appliances, including some digital cameras. It has the shape and size of two side-by-side AA batteries. This allows CR-V3 batteries to function in many devices originally designed only for AA batteries...
batteries, with AAA batteries
AAA battery
A triple A or AAA battery is a standard size of dry cell battery commonly used in portable electronic devices. A carbon-zinc battery in this size is designated by IEC as "R03", by ANSI C18.1 as "24", by old JIS standard as "UM 4", and by other manufacturer and national standard designations that...
in a handful of cameras. The CR2 and CR-V3 batteries are lithium based
Lithium battery
Lithium batteries are disposable batteries that have lithium metal or lithium compounds as an anode. Depending on the design and chemical compounds used, lithium cells can produce voltages from 1.5 V to about 3.7 V, over twice the voltage of an ordinary zinc–carbon battery or alkaline battery...
, and intended for single use. They are also commonly seen in camcorders. AA batteries are the most common; however, the non-rechargeable alkaline batteries supplied with low-end cameras are capable of powering most cameras for only a very short time. They may serve satisfactorily in cameras that are only occasionally used.
Consumers with more than an occasional need use AA Nickel metal hydride batteries
Nickel metal hydride battery
A nickel–metal hydride cell, abbreviated NiMH, is a type of rechargeable battery similar to the nickel–cadmium cell. The NiMH battery uses a hydrogen-absorbing alloy for the negative electrode instead of cadmium. As in NiCd cells, the positive electrode is nickel oxyhydroxide...
(NiMH) instead, which provide adequate energy and are rechargeable. NIMH batteries do not provide as much energy per volume as lithium ion batteries
Lithium ion battery
A lithium-ion battery is a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging. Chemistry, performance, cost, and safety characteristics vary across LIB types...
, and they also tend to discharge when not used. For the same energy, a NiMH rechargeable battery
Rechargeable battery
A rechargeable battery or storage battery is a group of one or more electrochemical cells. They are known as secondary cells because their electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging anything from a button cell to...
takes up to twice the volume of a Li-on rechargeable battery, and is three to five times heavier, but only costs half as much. Rechargeable batteries are available in various ampere-hour
Ampere-hour
An ampere-hour or amp-hour is a unit of electric charge, with sub-units milliampere-hour and milliampere second...
(Ah) or milli
Milli
Milli is a prefix in the metric system denoting a factor of one thousandth . Adopted in 1795, the prefix comes from the Latin mille, meaning one thousand ....
-ampere-hour (mAh) ratings, which are approximately proportional to shots per charge.
Typically mid-range consumer models and some low end cameras use off-the-shelf batteries; only a very few DSLR
Digital single-lens reflex camera
Most digital single-lens reflex cameras are digital cameras that use a mechanical mirror system and pentaprism to direct light from the lens to an optical viewfinder on the back of the camera....
cameras accept them (for example, Sigma SD10
Sigma SD10
The Sigma SD10 is a digital SLR camera produced by the Sigma Corporation of Japan. It was announced on October 27, 2003 and is an evolution of the previous SD9 model, addressing many of the shortcomings of that camera...
). Rechargeable RCR-V3 lithium-ion batteries are also available as an alternative to non-rechargeable CR-V3 batteries. Cameras, especially earlier ones made for AA-size batteries assumed that these would be of the non-rechargeable, preferably alkaline manganese type delivering 1.5 volts per cell. Rechargeable NiCd or NiMH cells only deliver 1.2 volts, which means that many such cameras will only operate for a short time or not at all even with new and newly charged 1.2 volt units. A portable ultra-high-endurance external power-supply for the shoulder bag to operate older 6 volt cameras can be made up of five 1.2 volt C-size cells which can be either NiCd or NiMH, with a cable and 4mm DC-plug.
Proprietary
The second type of battery for digital cameras is proprietary battery formats. These are built to a manufacturer's custom specifications, and can be either aftermarket replacement parts or OEMOriginal Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...
. Almost all proprietary batteries are lithium ion
Lithium ion battery
A lithium-ion battery is a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging. Chemistry, performance, cost, and safety characteristics vary across LIB types...
. While they only accept a certain number of recharges before the battery life begins degrading (typically up to 500 cycles), they provide considerable performance for their size. A result is that at the two ends of the spectrum both high end professional cameras and low end consumer models tend to use lithium ion batteries.
Conversion of film cameras to digital
When digital cameras became common, a question many photographers asked was whether their film cameras could be converted to digital. The answer was yes and no. For the majority of 35 mm film cameras the answer is no, the reworking and cost would be too great, especially as lenses have been evolving as well as cameras. For most a conversion to digital, to give enough space for the electronics and allow a liquid crystal display to preview, would require removing the back of the camera and replacing it with a custom built digital unit.Many early professional SLR cameras, such as the Kodak DCS
Kodak DCS
The Kodak Digital Camera System is a series of digital single-lens reflex cameras and digital camera backs that were released by Kodak in the 1990s and 2000s, and discontinued in 2005. They were all based on existing 35mm film SLRs from Nikon and Canon...
series, were developed from 35 mm film cameras. The technology of the time, however, meant that rather than being digital "backs" the bodies of these cameras were mounted on large, bulky digital units, often bigger than the camera portion itself. These were factory built cameras, however, not aftermarket conversions.
A notable exception is the Nikon E2, followed by Nikon E3
Nikon E3
The Nikon E3 and Nikon E3s, co-developed with Fujifilm and marketed also as the Fujix DS-565, are autofocus 1.3 megapixel professional grade quasi-full frame digital single lens reflex cameras announced by the Nikon Corporation on 15 June 1998 and released in December 1999. The E3S is identical...
, using additional optics to convert the 35mm format to a 2/3 CCD-sensor.
A few 35 mm cameras have had digital camera back
Digital camera back
A digital camera back is a device that attaches to the back of a camera in place of a film holder and contains an electronic image sensor. This lets cameras that were designed to use film take digital photographs...
s made by their manufacturer, Leica being a notable example. Medium format and large format
Large format
Large format refers to any imaging format of 4×5 inches or larger. Large format is larger than "medium format", the 6×6 cm or 6×9 cm size of Hasselblad, Rollei, Kowa, Pentax etc cameras , and much larger than the 24×36 mm frame of 35 mm format.The main advantage...
cameras (those using film stock greater than 35 mm), have a low unit production, and typical digital backs for them cost over $10,000. These cameras also tend to be highly modular, with handgrips, film backs, winders, and lenses available separately to fit various needs.
The very large sensor these backs use leads to enormous image sizes. For example Phase One's P45 39 MP image back creates a single TIFF image of size up to 224.6 MB, and even greater pixel counts are available. Medium format digitals such as this are geared more towards studio and portrait photography than their smaller DSLR counterparts; the ISO speed in particular tends to have a maximum of 400, versus 6400 for some DSLR cameras. (Canon EOS-1D Mark IV and Nikon D3S
Nikon D3S
The Nikon D3S is a 12.1 megapixel professional-grade full frame digital single-lens reflex camera announced by Nikon Corporation on 14 October 2009. The D3S is the fourth camera in Nikon's line to feature a full frame sensor, following the D3, D700 and D3X. It is also Nikon's first full frame...
have ISO 12800 plus Hi-3 ISO 102400 with the Canon EOS-1Dx's ISO of 204800)
Digital camera backs
In the industrial and high-end professional photography market, some camera systems utilize modular (removable) image sensors. For example, some medium format SLRSingle-lens reflex camera
A single-lens reflex camera is a camera that typically uses a semi-automatic moving mirror system that permits the photographer to see exactly what will be captured by the film or digital imaging system, as opposed to pre-SLR cameras where the view through the viewfinder could be significantly...
cameras, such as the Mamiya
Mamiya
is a Japanese company that today manufactures high-end cameras and other related photographic and optical equipment. With headquarters in Tokyo, it has two manufacturing plants and a workforce of over 200 people...
645D series, allow installation of either a digital camera back or a traditional photographic film back.
- Area array
- CCD
- CMOS
- Linear array
- CCD (monochrome)
- 3-strip CCD with color filters
Linear array cameras are also called scan backs.
- Single-shot
- Multi-shot (three-shot, usually)
Most earlier digital camera backs used linear array sensors. The linear array sensor acts like its counterpart in a flatbed image scanner
Image scanner
In computing, an image scanner—often abbreviated to just scanner—is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Common examples found in offices are variations of the desktop scanner where the document is placed on a glass...
by moving vertically to digitize the image. Many early such cameras only capture grayscale
Grayscale
In photography and computing, a grayscale or greyscale digital image is an image in which the value of each pixel is a single sample, that is, it carries only intensity information...
images. Color photography requires three separate scans, and a mechanical assembly to cycle a primary color filter in front of the sensor. These are called multi-shot backs. The entire scanning process requires relatively long expsoure times, in the range of seconds or even minutes. Due to this relatively long exposure-time, scanning and mutli-shot backs are generally limited to studio applications, where all aspects of the photographic scene are under the photographer's control.
Some other camera backs use CCD arrays similar to typical cameras. These are called single-shot backs.
Since it is much easier to manufacture a high-quality linear CCD array with only thousands of pixels than a CCD matrix with millions, very high resolution linear CCD camera backs were available much earlier than their CCD matrix counterparts. For example, you could buy an (albeit expensive) camera back with over 7,000 pixel horizontal resolution in the mid-1990s. However, , it is still difficult to buy a comparable CCD matrix camera of the same resolution. Rotating line cameras, with about 10,000 color pixels in its sensor line, are able, , to capture about 120,000 lines during one full 360 degree rotation, thereby creating a single digital image of 1,200 Megapixels.
Most modern digital camera backs use CCD or CMOS matrix sensors. The matrix sensor captures the entire image frame at once, instead of incrementing scanning the frame area through the prolonged exposure. For example, Phase One produces a 39 million pixel digital camera back with a 49.1 x 36.8 mm CCD in 2008. This CCD array is a little smaller than a frame of 120 film
120 film
120 is a film format for still photography introduced by Kodak for their Brownie No. 2 in 1901. It was originally intended for amateur photography but was later superseded in this role by 135 film...
and much larger than a 35 mm
35 mm film
35 mm film is the film gauge most commonly used for chemical still photography and motion pictures. The name of the gauge refers to the width of the photographic film, which consists of strips 35 millimeters in width...
frame (36 x 24 mm). In comparison, consumer digital cameras use arrays ranging from 36 x 24 mm (full frame on high end consumer DSLRs) to 7.2 x 5.3 mm (on point and shoot cameras) CMOS sensor.
At present, there are relatively few complete digital SLR cameras with sensors large enough to compete with the image detail offered by medium to large format film cameras. Phase One, Mamiya
Mamiya
is a Japanese company that today manufactures high-end cameras and other related photographic and optical equipment. With headquarters in Tokyo, it has two manufacturing plants and a workforce of over 200 people...
, and Hasselblad
Hasselblad
Victor Hasselblad AB is a Swedish manufacturer of medium-format cameras and photographic equipment based in Gothenburg, Sweden.The company is best known for the medium-format cameras it has produced since World War II....
in 2011 manufacture medium format digital devices that can capture 30MP up to 80MP. The units tend to be quite large and expensive. Additionally, because of their high build quality and lack of moving parts, they tend to be quite long lasting and are prominent on the used market.