Digital versus film photography
Encyclopedia
Digital versus film photography has been a topic of debate since the invention of digital camera
s towards the end of the 20th Century. Both digital
and film
photography have advantages and drawbacks. 21st century photography is dominated by digital operation, but the older photochemical
methods continue to serve many users and applications.
s) in the image sensor
is usually counted in millions and called "megapixels" and often used as a figure of merit
. The resolution of film images depends upon the area of film used to record the image (35 mm
, Medium format or Large format
) and the speed
. Resolution of both film and digital are subject to the quality of lens fitted to the camera
.
Digital cameras have a variable relationship between final output image resolution and sensor megapixel count; other factors are important in digital camera resolution, such as the number of pixels used to resolve the image, the effect of the Bayer pattern or other sensor filters on the digital sensor and the image processing algorithm used to interpolate sensor pixels to image pixels. Digital sensors are generally arranged in a rectangular grid pattern, making images susceptible to moire pattern
artifacts, whereas film is not affected by this because of the random orientation of its grains.
Estimates of a photograph's resolution taken with a 35 mm film camera vary. More information may be recorded if a fine-grain film
, combined with a specially formulated developer, are used. Conversely, use of poor quality optics or coarse-grained film yield lower image resolution . A 36 mm x 24 mm frame of ISO 100-speed film
was initially estimated to contain the equivalent of 20 million pixels,, although this estimation was later revised to between 4 and 16 million pixel depending on the type of film used.
Many professional-quality film cameras use medium format or large format
films. Because of the size of the imaging area, these can record higher resolution images than current top-of-the-range digital cameras. A medium format film image can record an equivalent of approximately 50 megapixels, while large format films can record around 200 megapixels (4 × 5 inch) which equates to around 800 megapixels on the largest common film format, 8 × 10 inches, without accounting for lens sharpness. A medium format DSLR provides from 42 to 50 megapixels, but cannot be enlarged with the same level of detail as medium format film.
Thus film and digital work each provide a wide range of performance in this regard, overlapping but with film tending to higher resolution.
The medium which will be used for display, and the viewing distance, should be taken into account. For instance, if a photograph will only be viewed on an old analog television or modern HDTV set of 1080p
that can resolve approximately 0.3 megapixel and 2 megapixels, respectively, the resolution provided by high-end camera phone
s may suffice, and inexpensive compact cameras usually will. Similar or more expensive hardware may also fill the screens of computer display
s, though those few that show tens of megapixels
will be out of reach of low-end film photography and all but specialized scientific or industrial digital cameras.
becomes obvious in areas of even and delicate tone. Grain and film sensitivity
are linked, with more sensitive films having more obvious grain. Likewise, when used at high sensitivity settings, digital camera images show more image noise
than those made at lower sensitivities.
However, even if both techniques have inherent noise, it is widely appreciated that for color, digital photography has much less noise/grain than film at equivalent sensitivity, leading to an edge in image quality. For black-and-white photography, grain takes a more positive role in image quality, and such comparisons are less valid.
Noise is a particularly critical issue with digital cameras, often producing colour distortion or confetti, occurring most severely on the blue component and least severely on the red component.
Nearly all digital cameras apply noise reduction
to long exposure photographs to counteract thermal noise. For very long exposures, the image sensor
must be operated at low temperatures to prevent noise affecting the final image. Film grain is not affected by exposure time, although the apparent speed of the film changes with lengthy exposures, a phenomenon known as reciprocity failure.
(DR) is a complex issue. Comparisons between film and digital media should consider:
Dynamic range is of considerable importance to image quality in both the digital and emulsion domain. Both film and digital sensors exhibit non-linear responses to the amount of light, and at the edges of the dynamic range, close to underexposure and overexposure the media will exhibit particularly non-linear responses. The non-linear dynamic response or saturation qualities of emulsion film are often considered a desirable effect by photographers, and the distortion of colour, contrast and brightness varies considerably between film stocks. There is no limit to the number of possible levels of colour on emulsion film, whereas a digital sensor stores integer numbers, producing a limited and specific possible number of colours. Banding may be visible in the unusual case that it is not obscured by noise, and detail may be lost, particularly in shadow and highlight areas.
Some amateur authors have performed tests with inconclusive results. R. N. Clark, comparing a professional digital camera with 35 mm film, concluded that "Digital cameras, like the Canon 1D Mark II, show a huge dynamic range compared to either print or slide film, at least for the films compared."
Ken Rockwell reached a different conclusion: "CCDs and the related capture electronics will need about ten times more dynamic range (three stops) than they have today to be able to simulate film's shoulder....This is the biggest image defect in digital cameras today."
Carson Wilson informally compared Kodak Gold 200 film with a Nikon D60
digital camera and concluded that "In this test a high-end consumer digicam fell short of normal consumer color print film in the area of dynamic range."
The digital camera industry is attempting to address the problem of dynamic range. Some cameras have an automatic exposure bracketing mode, to be used in conjunction with high dynamic range imaging
software. Some CCDs including Fujifilm
's Super CCD
combine photosites of different sizes to give increased dynamic range. Other manufacturers use in-camera software to prevent highlight overexposure. Nikon calls this feature D-Lighting.
Presentation technology is also relevant, as different color printing
methods, cathode-ray tubes, LCDs and other displays all have different dynamic range limits and degrees of linearity.
Almost all compact digital cameras, and most digital SLRs
or ILCs
, have sensors smaller than the 36 mm x 24 mm exposure-frame of "35 mm" film. This affects:
Depth of field
is often quoted as being greater for digital cameras than for film cameras. The maxim packages several counterintuitive aspects of photography into a single (largely correct) theorem.
Depth of field
, for a given lens focal length, at a given f-number
will scale with sensor (film/chip) size. In effect, a smaller sensor will increase the apparent depth of field because it magnifies the portion of the image that is in focus.
However, manufacturers are increasingly using (especially in the budget digital camera market) "35 millimeter equivalent" focal lengths for lenses. This gives rise to the "depth of field is greater for digital cameras" myth: the shorter the focal length of a lens, the greater is its depth of field (at fixed F-stop). Therefore, if a sensor that is one-fourth the width and height of a 24 x 36 mm frame of film is exposed to an image through a lens that is correspondingly one-fourth the focal length, the depth of field increases 16x (scaling per the square of focal length) on an absolute scale, but 4x from a comparison-of-images perspective (the imaging dimension is 4x smaller).
This increase in relative depth-of-field may have advantages for taking snapshot
s; more image will be in focus than with a larger sensor and an autofocus
system inaccuracies are less critical to produce an acceptable image. Contrarily, photographers wishing to decrease depth of field to create certain effects, such as isolating subjects from their background need to increase aperature when sensors smaller than 36 mm x 24 mm to achieve the same degree of selective focusing. Depth of field can be minimized by use of large format
cameras, which are very rarely digital.
Light sensitivity and pixel noise are both related to pixel size, which is in turn related to sensor size and resolution. As the resolution of sensors (of a specific format) increase, the size of the individual pixels naturally has to decrease. This smaller pixel size means that each pixel collects less light and the resulting signal must be amplified more to produce the final value. Noise is also amplified and the signal-to-noise ratio
decreases, and the higher noise floor
means that less useful information is extracted from the darker parts of the image.
Countering these effects of digital-signal noise are advances being made in sensor technology itself. Currently (2010) the top-end of digital sensor sensitivity is at ISO 102,400 (both Canon and Nikon), whereas the run-of-the-mill prosumer DSLR and ILC cameras offer sensitivities greater than ISO 6400, often with good noise performance at one-quarter maximum sensitivity.
Some digital SLRs use lens mount
s originally designed for film cameras. If the camera has a smaller imaging area than the lens' intended film frame, its field of view
is cropped. This crop factor
is often called a "focal length multiplier" because the effect can be calculated by multiplying the focal length of the lens. For lenses that are not designed for a smaller imaging area whilst using the 35 mm-compatible lens mount, this has the beneficial side effect of only using the centre part of the lens, where the image quality is in some aspects higher. Only expensive digital SLRs and very rarely expensive 'compacts' have 36mm × 24 mm sensors, eliminating depth of field and crop factor problems when compared to 35 mm film cameras.
The smaller sensor size of digital compact cameras means that prints are extreme enlargements of the original image, and that the lens must perform well in order to provide enough resolution to match the tiny pixels on the sensor. Most digital compacts have sensors that exceed the maximum resolution that the lens is capable of delivering. Increased sensor resolution may have an effect upon the image resolution because of increased noise reduction.
Compact digital cameras are fitted with fixed lenses; dust is excluded from the imaging area. Similar film cameras are often only light-tight and not environmentally sealed. Some modern DSLRs, like the Olympus E-3, incorporate extensive dust and weather seals to avoid this problem.
or visa photographs, film provides greater security over most digital cameras, as digital files may have been modified using a computer. However, some digital cameras can produce authenticated images. If someone modifies an authenticated image, it can be determined with special software. SanDisk
claims to have developed a write-once memory stick
for cameras, and that the images once written cannot be altered.
From an artistically conservative standpoint, some practitioners believe that the use of film offers a more authentic
mode of expression than with easily enhanced digital images. As with the earlier transition from oil painting
to photography, or from photographic plate
s to film photography, older methods are more expensive, thus encourage more selectivity and additional consideration.
s can make low-quality prints cheaply and easily from digital files, but high-quality printing has high costs regardless of image source.
, after which they may be manipulated as digital images. Several methods are available:
or platinum
toned prints
may have a lifespan limited by that of the base material.
The archival potential of digital images is poorly understood because digital media have existed for 50 years. The physical stability of the recording medium, future readability of the storage medium and future readability of the file format
s used for storage are issues to be considered. Some types of digital media are incapable of storing data for prolonged periods. According to proponents of digital media magnetic disks and tapes will lose their data after twenty years, although in practice properly stored magnetic media will last far longer, perhaps hundreds of years. However flash memory cards may lose their data in fewer than twenty years. Good quality optical media may be the most durable digital storage media.
It is important to consider the future readability of storage media. Assuming the storage media can continue to hold data for prolonged periods of time. The equipment necessary to read media may become unavailable. For example, 5¼-inch floppy disk
s were first made available in 1976 but the drives to read them are already extremely rare. Also lower density floppy disk formats (e.g. 360k) prove to be more readily readable 25 years later.
The ability to decode the data is important. Digital cameras save photographs in JPEG format, which has existed for approximately 15 years. Because the instructions on how to decode this format are publicly known, it is likely that these files will be readable in the future.
Most professional cameras can save in a Raw image format
, the future of which is less certain. Some of these formats contain proprietary data which is encrypted or protected by patent
s, and could be abandoned by their makers for economic or other reasons, causing possible future difficulty in decoding these files unless the camera makers were to release information on the file formats.
In order to counteract the file format problems, many organizations prefer to choose an open
and popular file format, increasing the chance that software will exist to decode the file in the future. Many organizations take an active approach to archiving rather than relying on the future readability of digital files, relying upon the ability to make perfect copies of digital media. Rather than leaving data on in format which may potentially become unreadable or unsupported, the information can be copied to newer media without loss of quality. Digital images may also be printed and stored like other printed photos.
Flexibility and convenience are among the reasons for the widespread adoption of digital cameras. With film cameras, a roll is usually completely exposed before being processed. When the film is returned it is possible to see the photograph, but most digital cameras incorporate a liquid crystal display
that allows the image to be viewed immediately after capture. The photographer may delete undesired or unnecessary photographs, or reshoot the image if required. A user who wants prints can quickly and easily print just the required photographs.
Photographic film is made with specific characteristics of Color temperature
and sensitivity
(ISO). Lighting conditions often require characteristics different from those of the film specifications, requiring the use of filters
or corrections in processing
. Digital photography allows color temperature and sensitivity to be adjusted at each shot, either manually or automatically.
Digital images may be conveniently stored on a personal computer or in off-line storage such as small memory card
s. Professional-grade digital cameras can store pictures in a raw image format
, which stores the output from the sensor rather than processing it immediately to form an image. When edited in suitable software, such as Adobe Photoshop
or the GNU program GIMP
(which uses dcraw
to read raw files), the user may manipulate certain parameters, such as contrast, sharpness or color balance
before producing an image. JPEG
images can be similarly manipulated, though usually less precisely; software for this purpose may be provided with consumer-grade cameras.
Digital photography allows the quick collection of a large quantity of archival documents, bringing convenience, lower cost and increased flexibility in using the documents.
For large format
and ultra large format photography, film may have some advantages over digital cameras, such as price and flexibility, when used outside the studio
environment. Digital rotating line camera
s provide similarly high performance, but scan mechanically rather than use a single sensor, making them expensive, large, and rarely moved.
Digital camera
A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...
s towards the end of the 20th Century. Both digital
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...
and film
Photographic film
Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...
photography have advantages and drawbacks. 21st century photography is dominated by digital operation, but the older photochemical
Photochemistry
Photochemistry, a sub-discipline of chemistry, is the study of chemical reactions that proceed with the absorption of light by atoms or molecules.. Everyday examples include photosynthesis, the degradation of plastics and the formation of vitamin D with sunlight.-Principles:Light is a type of...
methods continue to serve many users and applications.
Spatial resolution
The quality of digital photographs can be measured in several ways. Pixel count is presumed to correlate with spatial resolution. The quantity of picture elements (pixelPixel
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....
s) in 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...
is usually counted in millions and called "megapixels" and often used as a 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...
. The resolution of film images depends upon the area of film used to record the image (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...
, Medium format or 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...
) and the speed
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....
. Resolution of both film and digital are subject to the quality of lens fitted to the camera
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...
.
Digital cameras have a variable relationship between final output image resolution and sensor megapixel count; other factors are important in digital camera resolution, such as the number of pixels used to resolve the image, the effect of the Bayer pattern or other sensor filters on the digital sensor and the image processing algorithm used to interpolate sensor pixels to image pixels. Digital sensors are generally arranged in a rectangular grid pattern, making images susceptible to moire pattern
Moiré pattern
In physics, a moiré pattern is an interference pattern created, for example, when two grids are overlaid at an angle, or when they have slightly different mesh sizes.- Etymology :...
artifacts, whereas film is not affected by this because of the random orientation of its grains.
Estimates of a photograph's resolution taken with a 35 mm film camera vary. More information may be recorded if a fine-grain film
Film grain
Film grain or granularity is the random optical texture of processed photographic film due to the presence of small particles of a metallic silver, or dye clouds, developed from silver halide that have received enough photons. While film grain is a function of such particles it is not the same...
, combined with a specially formulated developer, are used. Conversely, use of poor quality optics or coarse-grained film yield lower image resolution . A 36 mm x 24 mm frame of ISO 100-speed film
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....
was initially estimated to contain the equivalent of 20 million pixels,, although this estimation was later revised to between 4 and 16 million pixel depending on the type of film used.
Many professional-quality film cameras use medium format or 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...
films. Because of the size of the imaging area, these can record higher resolution images than current top-of-the-range digital cameras. A medium format film image can record an equivalent of approximately 50 megapixels, while large format films can record around 200 megapixels (4 × 5 inch) which equates to around 800 megapixels on the largest common film format, 8 × 10 inches, without accounting for lens sharpness. A medium format DSLR provides from 42 to 50 megapixels, but cannot be enlarged with the same level of detail as medium format film.
Thus film and digital work each provide a wide range of performance in this regard, overlapping but with film tending to higher resolution.
The medium which will be used for display, and the viewing distance, should be taken into account. For instance, if a photograph will only be viewed on an old analog television or modern HDTV set of 1080p
1080p
1080p is the shorthand identification for a set of HDTV high-definition video modes that are characterized by 1080 horizontal lines of resolution and progressive scan, meaning the image is not interlaced as is the case with the 1080i display standard....
that can resolve approximately 0.3 megapixel and 2 megapixels, respectively, the resolution provided by high-end 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 may suffice, and inexpensive compact cameras usually will. Similar or more expensive hardware may also fill the screens of computer display
Computer display
A monitor or display is an electronic visual display for computers. The monitor comprises the display device, circuitry, and an enclosure...
s, though those few that show tens of megapixels
Graphic display resolutions
The graphics display resolution describes the width and height dimensions of a display, such as a computer monitor, in pixels. Certain combinations of width and height are standardized and typically given a name and an initialism that is descriptive of its dimensions...
will be out of reach of low-end film photography and all but specialized scientific or industrial digital cameras.
Noise and grain
Thermal noise, produced by heat and manufacturing defects, degrades shadow areas of electronic images with random pixels of the incorrect colour. Film grainFilm grain
Film grain or granularity is the random optical texture of processed photographic film due to the presence of small particles of a metallic silver, or dye clouds, developed from silver halide that have received enough photons. While film grain is a function of such particles it is not the same...
becomes obvious in areas of even and delicate tone. Grain and film sensitivity
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....
are linked, with more sensitive films having more obvious grain. Likewise, when used at high sensitivity settings, digital camera images show more 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...
than those made at lower sensitivities.
However, even if both techniques have inherent noise, it is widely appreciated that for color, digital photography has much less noise/grain than film at equivalent sensitivity, leading to an edge in image quality. For black-and-white photography, grain takes a more positive role in image quality, and such comparisons are less valid.
Noise is a particularly critical issue with digital cameras, often producing colour distortion or confetti, occurring most severely on the blue component and least severely on the red component.
Nearly all digital cameras apply noise reduction
Noise reduction
Noise reduction is the process of removing noise from a signal.All recording devices, both analogue or digital, have traits which make them susceptible to noise...
to long exposure photographs to counteract thermal noise. For very long exposures, 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...
must be operated at low temperatures to prevent noise affecting the final image. Film grain is not affected by exposure time, although the apparent speed of the film changes with lengthy exposures, a phenomenon known as reciprocity failure.
Dynamic range
Dynamic rangeDynamic range
Dynamic range, abbreviated DR or DNR, is the ratio between the largest and smallest possible values of a changeable quantity, such as in sound and light. It is measured as a ratio, or as a base-10 or base-2 logarithmic value.-Dynamic range and human perception:The human senses of sight and...
(DR) is a complex issue. Comparisons between film and digital media should consider:
- Film type: For example, low-contrast print film has greater dynamic range than slide film's low dynamic range and higher contrast.
- Data format: Raw image formatRAW image formatA 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 JPEGJPEGIn 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....
? - Pixel density of the sensor: The large sensors in DSLRs and medium format digital cameras generally have larger photosites which collect more light and therefore are generally more sensitive than their diminutive counterparts in compact digital cameras. The larger sensors tend to have better signal to noise characteristics. However signal processing and amplification improves with generation and small sensors of today approach the dynamic range of large sensors in the past.
- Scanner: Variations in optics, sensor resolution, scanner dynamic range and precision of the analogue to digital conversion circuit cause variations in image quality.
- Optical versus digital prints: Prints differ between media and between images shown on VDUVDUVDU may stand for:*Federation of Independents *Visual Display Unit*Vytauto Didžiojo Universitetas , in the city of Kaunas ....
s. - Signal/noise ratio: This defines the limits of dynamic range within a single photograph, and may vary with subject matter. A single comparison cannot demonstrate that digital or film has a smaller or greater dynamic range.
Dynamic range is of considerable importance to image quality in both the digital and emulsion domain. Both film and digital sensors exhibit non-linear responses to the amount of light, and at the edges of the dynamic range, close to underexposure and overexposure the media will exhibit particularly non-linear responses. The non-linear dynamic response or saturation qualities of emulsion film are often considered a desirable effect by photographers, and the distortion of colour, contrast and brightness varies considerably between film stocks. There is no limit to the number of possible levels of colour on emulsion film, whereas a digital sensor stores integer numbers, producing a limited and specific possible number of colours. Banding may be visible in the unusual case that it is not obscured by noise, and detail may be lost, particularly in shadow and highlight areas.
Some amateur authors have performed tests with inconclusive results. R. N. Clark, comparing a professional digital camera with 35 mm film, concluded that "Digital cameras, like the Canon 1D Mark II, show a huge dynamic range compared to either print or slide film, at least for the films compared."
Ken Rockwell reached a different conclusion: "CCDs and the related capture electronics will need about ten times more dynamic range (three stops) than they have today to be able to simulate film's shoulder....This is the biggest image defect in digital cameras today."
Carson Wilson informally compared Kodak Gold 200 film with a Nikon D60
Nikon D60
The Nikon D60 is a 10.2 megapixel Nikon F-mount digital single-lens reflex camera announced in January 2008. The D60 succeeds the entry-level Nikon D40x...
digital camera and concluded that "In this test a high-end consumer digicam fell short of normal consumer color print film in the area of dynamic range."
The digital camera industry is attempting to address the problem of dynamic range. Some cameras have an automatic exposure bracketing mode, to be used in conjunction with high dynamic range imaging
High dynamic range imaging
In image processing, computer graphics, and photography, high dynamic range imaging is a set of techniques that allows a greater dynamic range between the lightest and darkest areas of an image than current standard digital imaging techniques or photographic methods...
software. Some CCDs including 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...
's Super CCD
Super CCD
Super CCD is a proprietary charge-coupled device that has been developed by Fujifilm since 1999. The Super CCD uses octagonal, rather than rectangular, pixels...
combine photosites of different sizes to give increased dynamic range. Other manufacturers use in-camera software to prevent highlight overexposure. Nikon calls this feature D-Lighting.
Presentation technology is also relevant, as different color printing
Color printing
Color printing or Colour printing is the reproduction of an image or text in color...
methods, cathode-ray tubes, LCDs and other displays all have different dynamic range limits and degrees of linearity.
Effects of sensor size
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....
or ILCs
Mirrorless interchangeable lens camera
A mirrorless interchangeable-lens camera is an emerging class of digital system cameras, intermediate between compact digital cameras and digital single-lens reflex cameras . They are characterized by a no-mirror design and an interchangeable lens mount...
, have sensors smaller than the 36 mm x 24 mm exposure-frame of "35 mm" film. This affects:
- Depth of field;
- Light sensitivity and pixel noise;
- Relative cropping of the field of view when using lenses designed for 35 mm camera;
- Optimizing lens design for smaller sensor area;
- Increased relative enlargement of the captured image.
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...
is often quoted as being greater for digital cameras than for film cameras. The maxim packages several counterintuitive aspects of photography into a single (largely correct) theorem.
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...
, for a given lens focal length, at a given f-number
F-number
In optics, the f-number of an optical system expresses the diameter of the entrance pupil in terms of the focal length of the lens; in simpler terms, the f-number is the focal length divided by the "effective" aperture diameter...
will scale with sensor (film/chip) size. In effect, a smaller sensor will increase the apparent depth of field because it magnifies the portion of the image that is in focus.
However, manufacturers are increasingly using (especially in the budget digital camera market) "35 millimeter equivalent" focal lengths for lenses. This gives rise to the "depth of field is greater for digital cameras" myth: the shorter the focal length of a lens, the greater is its depth of field (at fixed F-stop). Therefore, if a sensor that is one-fourth the width and height of a 24 x 36 mm frame of film is exposed to an image through a lens that is correspondingly one-fourth the focal length, the depth of field increases 16x (scaling per the square of focal length) on an absolute scale, but 4x from a comparison-of-images perspective (the imaging dimension is 4x smaller).
This increase in relative depth-of-field may have advantages for taking snapshot
Snapshot
Snapshot may refer to:* Snapshot , an amateur photograph* Snapshot, a 1979 Australian film directed by Simon Wincer* Snapshot, a novel by Garry Disher...
s; more image will be in focus than with a larger sensor and an 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 inaccuracies are less critical to produce an acceptable image. Contrarily, photographers wishing to decrease depth of field to create certain effects, such as isolating subjects from their background need to increase aperature when sensors smaller than 36 mm x 24 mm to achieve the same degree of selective focusing. Depth of field can be minimized by use of 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, which are very rarely digital.
Light sensitivity and pixel noise are both related to pixel size, which is in turn related to sensor size and resolution. As the resolution of sensors (of a specific format) increase, the size of the individual pixels naturally has to decrease. This smaller pixel size means that each pixel collects less light and the resulting signal must be amplified more to produce the final value. Noise is also amplified and the signal-to-noise ratio
Signal-to-noise ratio
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
decreases, and the higher noise floor
Noise floor
In signal theory, the noise floor is the measure of the signal created from the sum of all the noise sources and unwanted signals within a measurement system, where the noise is defined as any signal other than the one being monitored....
means that less useful information is extracted from the darker parts of the image.
Countering these effects of digital-signal noise are advances being made in sensor technology itself. Currently (2010) the top-end of digital sensor sensitivity is at ISO 102,400 (both Canon and Nikon), whereas the run-of-the-mill prosumer DSLR and ILC cameras offer sensitivities greater than ISO 6400, often with good noise performance at one-quarter maximum sensitivity.
Some digital SLRs use lens mount
Lens mount
A lens mount is an interface — mechanical and often also electrical — between a photographic camera body and a lens. It is confined to cameras where the body allows interchangeable lenses, most usually the single lens reflex type or any movie camera of 16 mm or higher gauge...
s originally designed for film cameras. If the camera has a smaller imaging area than the lens' intended film frame, its field of view
Field of view
The field of view is the extent of the observable world that is seen at any given moment....
is cropped. This 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...
is often called a "focal length multiplier" because the effect can be calculated by multiplying the focal length of the lens. For lenses that are not designed for a smaller imaging area whilst using the 35 mm-compatible lens mount, this has the beneficial side effect of only using the centre part of the lens, where the image quality is in some aspects higher. Only expensive digital SLRs and very rarely expensive 'compacts' have 36mm × 24 mm sensors, eliminating depth of field and crop factor problems when compared to 35 mm film cameras.
The smaller sensor size of digital compact cameras means that prints are extreme enlargements of the original image, and that the lens must perform well in order to provide enough resolution to match the tiny pixels on the sensor. Most digital compacts have sensors that exceed the maximum resolution that the lens is capable of delivering. Increased sensor resolution may have an effect upon the image resolution because of increased noise reduction.
Cleanliness
Dust on the image plane is a constant issue for photographers. DSLR cameras are especially prone to dust problems because the sensor remains in place, where a film advances through the camera for each exposure. Debris in the camera, such as dust or sand, may scratch the film; a single grain of sand can damage a whole roll of film. As film cameras age, they can develop burs in their rollers. With a digital SLR, dust is difficult to avoid but is easy to rectify using a computer with image-editing software. Some digital SLRs have systems that remove dust from the sensor by vibrating or knocking it, sometimes in conjunction with software that remembers where dust is located and removes dust-affected pixels from images.Compact digital cameras are fitted with fixed lenses; dust is excluded from the imaging area. Similar film cameras are often only light-tight and not environmentally sealed. Some modern DSLRs, like the Olympus E-3, incorporate extensive dust and weather seals to avoid this problem.
Integrity
Film produces a first generation image, which contains only the information admitted through the aperture of the camera. Trick photography is more difficult with film; in law enforcement and where the authenticity of an image is important, like passportPassport
A passport is a document, issued by a national government, which certifies, for the purpose of international travel, the identity and nationality of its holder. The elements of identity are name, date of birth, sex, and place of birth....
or visa photographs, film provides greater security over most digital cameras, as digital files may have been modified using a computer. However, some digital cameras can produce authenticated images. If someone modifies an authenticated image, it can be determined with special software. SanDisk
SanDisk
SanDisk Corporation is an American multinational corporation that designs, develops and manufactures data storage solutions in a range of form factors using the flash memory, controller and firmware technologies. It was founded in 1988 by Dr. Eli Harari and Sanjay Mehrotra, non-volatile memory...
claims to have developed a write-once memory stick
Memory Stick
Memory Stick is a removable flash memory card format, launched by Sony in October 1998, and is also used in general to describe the whole family of Memory Sticks...
for cameras, and that the images once written cannot be altered.
Authentication
Authentication is the act of confirming the truth of an attribute of a datum or entity...
mode of expression than with easily enhanced digital images. As with the earlier transition from oil painting
Oil painting
Oil painting is the process of painting with pigments that are bound with a medium of drying oil—especially in early modern Europe, linseed oil. Often an oil such as linseed was boiled with a resin such as pine resin or even frankincense; these were called 'varnishes' and were prized for their body...
to photography, or from photographic plate
Photographic plate
Photographic plates preceded photographic film as a means of photography. A light-sensitive emulsion of silver salts was applied to a glass plate. This form of photographic material largely faded from the consumer market in the early years of the 20th century, as more convenient and less fragile...
s to film photography, older methods are more expensive, thus encourage more selectivity and additional consideration.
Cost
Film and digital imaging systems have different cost emphases. Digital cameras are significantly more expensive than film equivalents, but taking photographs with them is effectively cost-free. Other costs of digital photography include specialist batteries, memory cards and long-term data storage. Inkjet printerInkjet printer
An inkjet printer is a type of computer printer that creates a digital image by propelling droplets of ink onto paper. Inkjet printers are the most commonly used type of printer and range from small inexpensive consumer models to very large professional machines that can cost up to thousands of...
s can make low-quality prints cheaply and easily from digital files, but high-quality printing has high costs regardless of image source.
Converting film to digital
Film photographs may be scanned into a computer with a scannerImage 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...
, after which they may be manipulated as digital images. Several methods are available:
- A reflective image scanner may be used; inexpensive flatbed scanners can scan an image on paper media.
- An expensive and very high resolution drum scanner can scan reflective and transparent media, and often uses a vacuum tube called a "photomultiplierPhotomultiplierPhotomultiplier tubes , members of the class of vacuum tubes, and more specifically phototubes, are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum...
" which exhibits much less noise and greater vibrancy than a CCD. - A Flying spot scannerFlying spot scannerA flying-spot scanner uses a scanning source of a spot of light, such as a high-resolution, high-light-output, low-persistence Cathode Ray Tube , to scan an image, usually from motion picture film or a slide...
can scan reels of film quickly. - A dedicated film scannerFilm scannerA film scanner is a device made for scanning photographic film directly into a computer without the use of any intermediate printmaking. It provides several benefits over using a flatbed scanner to scan in a print of any size: the photographer has direct control over cropping and aspect ratio from...
, such as the Nikon Coolscan (pictured), can scan 35 mm transparencies and negatives. Other film scanners can scan 120 film120 film120 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...
, typically up to 6 x 7 cm or 6 x 9 cm. - A digital camera on a copy standCopy standIn photography, a copy stand is a device used to copy images and/or text with a camera. The stand consists of a board onto which the media is placed and a tripod-mount parallel to it, usually with an adjustable height. Light is provided by bright lamps mounted on either side of the media at...
can photograph the source image. - A slide projectorSlide projectorA slide projector is an opto-mechanical device to view photographic slides. Slide projectors were common in the 1950s to the 1970s as a form of entertainment; family members and friends would gather to view slide shows...
can project the image from a transparency onto a screen, so the digital camera can photograph it.
Archiving
Films and prints, processed and stored in ideal conditions, may remain substantially unchanged for more than 100 years. GoldGold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
or platinum
Platinum
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
toned prints
Photographic print toning
In photography, toning is a method of changing the color of black-and-white photographs. In analog photography, toning is a chemical process carried out on silver-based photographic prints. This darkroom process can not be done with a color photograph and although the black-and-white photograph is...
may have a lifespan limited by that of the base material.
The archival potential of digital images is poorly understood because digital media have existed for 50 years. The physical stability of the recording medium, future readability of the storage medium and future readability of the file format
File format
A file format is a particular way that information is encoded for storage in a computer file.Since a disk drive, or indeed any computer storage, can store only bits, the computer must have some way of converting information to 0s and 1s and vice-versa. There are different kinds of formats for...
s used for storage are issues to be considered. Some types of digital media are incapable of storing data for prolonged periods. According to proponents of digital media magnetic disks and tapes will lose their data after twenty years, although in practice properly stored magnetic media will last far longer, perhaps hundreds of years. However flash memory cards may lose their data in fewer than twenty years. Good quality optical media may be the most durable digital storage media.
It is important to consider the future readability of storage media. Assuming the storage media can continue to hold data for prolonged periods of time. The equipment necessary to read media may become unavailable. For example, 5¼-inch floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
s were first made available in 1976 but the drives to read them are already extremely rare. Also lower density floppy disk formats (e.g. 360k) prove to be more readily readable 25 years later.
The ability to decode the data is important. Digital cameras save photographs in JPEG format, which has existed for approximately 15 years. Because the instructions on how to decode this format are publicly known, it is likely that these files will be readable in the future.
Most professional cameras can save 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...
, the future of which is less certain. Some of these formats contain proprietary data which is encrypted or protected by patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
s, and could be abandoned by their makers for economic or other reasons, causing possible future difficulty in decoding these files unless the camera makers were to release information on the file formats.
In order to counteract the file format problems, many organizations prefer to choose an open
Open format
An open file format is a published specification for storing digital data, usually maintained by a standards organization, which can therefore be used and implemented by anyone. For example, an open format can be implementable by both proprietary and free and open source software, using the typical...
and popular file format, increasing the chance that software will exist to decode the file in the future. Many organizations take an active approach to archiving rather than relying on the future readability of digital files, relying upon the ability to make perfect copies of digital media. Rather than leaving data on in format which may potentially become unreadable or unsupported, the information can be copied to newer media without loss of quality. Digital images may also be printed and stored like other printed photos.
Convenience and flexibility
Liquid crystal display
A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....
that allows the image to be viewed immediately after capture. The photographer may delete undesired or unnecessary photographs, or reshoot the image if required. A user who wants prints can quickly and easily print just the required photographs.
Photographic film is made with specific characteristics of Color temperature
Color temperature
Color temperature is a characteristic of visible light that has important applications in lighting, photography, videography, publishing, manufacturing, astrophysics, and other fields. The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of...
and sensitivity
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....
(ISO). Lighting conditions often require characteristics different from those of the film specifications, requiring the use of filters
Photographic filter
In photography and videography, a filter is a camera accessory consisting of an optical filter that can be inserted in the optical path. The filter can be a square or oblong shape mounted in a holder accessory, or, more commonly, a glass or plastic disk with a metal or plastic ring frame, which...
or corrections in processing
Photographic processing
Photographic processing is the chemical means by which photographic film and paper is treated after photographic exposure to produce a negative or positive image...
. Digital photography allows color temperature and sensitivity to be adjusted at each shot, either manually or automatically.
Digital images may be conveniently stored on a personal computer or in off-line storage such as small 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. Professional-grade digital cameras can store pictures 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...
, which stores the output from the sensor rather than processing it immediately to form an image. When edited in suitable software, such as Adobe Photoshop
Adobe Photoshop
Adobe Photoshop is a graphics editing program developed and published by Adobe Systems Incorporated.Adobe's 2003 "Creative Suite" rebranding led to Adobe Photoshop 8's renaming to Adobe Photoshop CS. Thus, Adobe Photoshop CS5 is the 12th major release of Adobe Photoshop...
or the GNU program GIMP
GIMP
GIMP is a free software raster graphics editor. It is primarily employed as an image retouching and editing tool and is freely available in versions tailored for most popular operating systems including Microsoft Windows, Apple Mac OS X, and Linux.In addition to detailed image retouching and...
(which uses dcraw
Dcraw
dcraw is an open-source computer program which is able to read numerous raw image formats, typically produced by high-end digital cameras. dcraw converts these images into the standard PPM and TIFF image formats...
to read raw files), the user may manipulate certain parameters, such as contrast, sharpness or color balance
Color balance
In photography and image processing, color balance is the global adjustment of the intensities of the colors . An important goal of this adjustment is to render specific colors – particularly neutral colors – correctly; hence, the general method is sometimes called gray balance, neutral balance,...
before producing an image. 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....
images can be similarly manipulated, though usually less precisely; software for this purpose may be provided with consumer-grade cameras.
Digital photography allows the quick collection of a large quantity of archival documents, bringing convenience, lower cost and increased flexibility in using the documents.
For 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...
and ultra large format photography, film may have some advantages over digital cameras, such as price and flexibility, when used outside the studio
Photographic studio
A photographic studio is both a workspace and a corporate body. As a workspace it is much like an artist’s studio, but providing space to take, develop, print and duplicate photographs. Photographic training and the display of finished photographs may also be accommodated in a photographic studio...
environment. 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...
s provide similarly high performance, but scan mechanically rather than use a single sensor, making them expensive, large, and rarely moved.