DPX
Encyclopedia
Digital Picture Exchange (DPX) is a common file format
for digital intermediate
and visual effects
work and is an ANSI
/SMPTE standard (268M-2003). The file format is most commonly used to represent the density of each colour channel of a scanned negative film in an uncompressed "logarithmic
" image where the gamma
of the original camera negative
is preserved as taken by a film scanner
. For this reason, DPX is the worldwide-chosen format for still frames storage in most Digital Intermediate
post-production facilities and film labs. Other common video formats are supported as well (see below), from video to purely digital ones, making DPX a file format suitable for almost any raster digital imaging applications. DPX provides, in fact, a great deal of flexibility in storing colour information, colour spaces and colour planes for exchange between production facilities. Multiple forms of packing and alignment are possible.
Last but not least, the DPX Specification allow for a wide variety of metadata to further clarity information stored (and storable) within each file.
The DPX file format was originally derived from Kodak Cineon
open file format (
, has then been improved and its latest version (2.0) is currently published by SMPTE as ANSI/SMPTE 268M-2003. Original DPX specifications version 1.0 are part of SMPTE 268M-1994).
details (channel depth, colorimetric metric, etc.), number of planes/subimages, as well as original filename and creation date/time, creator's name, project name, copyright
information, and so on.
Furthermore a couple of industry-specific metadata areas are present: Motion-Picture and Television ones. They are either used only if the picture has enough embedded information relevant to that specific industry, otherwise are left "empty".
For example, Motion-Picture-specific metadata include perforation-exact film KeyKode
(if the image comes from a film scan), camera shutter angle, slate information and frame positioning within a frame sequence
. On the other side, Television metadata include full SMPTE time code
, video overscan and field information, and signal/colour level information.
At last, a third, variable-size metadata area, which is user-definable, exists. Third-party applications/software occasionally use this area to store additional information; for example, when the DPX stores images with technical specifications far away from the original standard (like pictures coded in the CIE
XYZ
color space, or Bayer
-patterned raw frames from specific digital cameras like the Arriflex D-21
).
DPX is defined in SMPTE standard number 268M-2003, available in their store.
With Other SMPTE Standards:
SMPTE's website also has information about the ordering of CD-ROMs, which contains SMPTE standards including the SMPTE 268M-2003 standard.
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...
for digital intermediate
Digital intermediate
Digital intermediate is a motion picture finishing process which classically involves digitizing a motion picture and manipulating the color and other image characteristics. It often replaces or augments the photochemical timing process and is usually the final creative adjustment to a movie...
and visual effects
Visual effects
Visual effects are the various processes by which imagery is created and/or manipulated outside the context of a live action shoot. Visual effects involve the integration of live-action footage and generated imagery to create environments which look realistic, but would be dangerous, costly, or...
work and is an ANSI
American National Standards Institute
The American National Standards Institute is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organization also coordinates U.S. standards with international...
/SMPTE standard (268M-2003). The file format is most commonly used to represent the density of each colour channel of a scanned negative film in an uncompressed "logarithmic
Logarithmic scale
A logarithmic scale is a scale of measurement using the logarithm of a physical quantity instead of the quantity itself.A simple example is a chart whose vertical axis increments are labeled 1, 10, 100, 1000, instead of 1, 2, 3, 4...
" image where the gamma
Gamma correction
Gamma correction, gamma nonlinearity, gamma encoding, or often simply gamma, is the name of a nonlinear operation used to code and decode luminance or tristimulus values in video or still image systems...
of the original camera negative
Original camera negative
The original camera negative is the film in a motion picture camera which captures the original image. This is the film from which all other copies will be made. It is known as raw stock prior to exposure....
is preserved as taken by a film scanner
Film scanner
A 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...
. For this reason, DPX is the worldwide-chosen format for still frames storage in most Digital Intermediate
Digital intermediate
Digital intermediate is a motion picture finishing process which classically involves digitizing a motion picture and manipulating the color and other image characteristics. It often replaces or augments the photochemical timing process and is usually the final creative adjustment to a movie...
post-production facilities and film labs. Other common video formats are supported as well (see below), from video to purely digital ones, making DPX a file format suitable for almost any raster digital imaging applications. DPX provides, in fact, a great deal of flexibility in storing colour information, colour spaces and colour planes for exchange between production facilities. Multiple forms of packing and alignment are possible.
Last but not least, the DPX Specification allow for a wide variety of metadata to further clarity information stored (and storable) within each file.
The DPX file format was originally derived from Kodak Cineon
Cineon
Cineon System was a computer based system, integrating a film scanner and recorder hardware, digital software for compositing and effects, image restoration, color management and the development of a proprietary file format designed by Kodak. These components were created to support the work flow...
open file format (
.cin file extension) used for digital images generated by its original film scannerFilm scanner
A 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...
, has then been improved and its latest version (2.0) is currently published by SMPTE as ANSI/SMPTE 268M-2003. Original DPX specifications version 1.0 are part of SMPTE 268M-1994).
Metadata and Standard Flexibility
SMPTE Specifications dictate a mild number of compulsory metadata, like image resolution, color spaceColor space
A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components...
details (channel depth, colorimetric metric, etc.), number of planes/subimages, as well as original filename and creation date/time, creator's name, project name, copyright
Copyright
Copyright is a legal concept, enacted by most governments, giving the creator of an original work exclusive rights to it, usually for a limited time...
information, and so on.
Furthermore a couple of industry-specific metadata areas are present: Motion-Picture and Television ones. They are either used only if the picture has enough embedded information relevant to that specific industry, otherwise are left "empty".
For example, Motion-Picture-specific metadata include perforation-exact film KeyKode
Keykode
KeyKode is an Eastman Kodak Company advancement on edge numbers, which are letters, numbers and symbols placed at regular intervals along the edge of 35 mm and 16 mm film to allow for frame-by-frame specific identification...
(if the image comes from a film scan), camera shutter angle, slate information and frame positioning within a frame sequence
File sequence
In computing, as well as in non-computing contexts, a file sequence is a well-ordered, collection of files, usually related to each other in some way....
. On the other side, Television metadata include full SMPTE time code
SMPTE time code
SMPTE timecode is a set of cooperating standards to label individual frames of video or film with a time code defined by the Society of Motion Picture and Television Engineers in the SMPTE 12M specification...
, video overscan and field information, and signal/colour level information.
At last, a third, variable-size metadata area, which is user-definable, exists. Third-party applications/software occasionally use this area to store additional information; for example, when the DPX stores images with technical specifications far away from the original standard (like pictures coded in the CIE
International Commission on Illumination
The International Commission on Illumination is the international authority on light, illumination, color, and color spaces...
XYZ
CIE 1931 color space
In the study of color perception, one of the first mathematically defined color spaces is the CIE 1931 XYZ color space, created by the International Commission on Illumination in 1931....
color space, or Bayer
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...
-patterned raw frames from specific digital cameras like the Arriflex D-21
Arriflex D-21
The Arriflex D-21 is a film-style digital motion picture camera introduced by Arri in 2008 to replace their earlier generation Arriflex D-20.- Overview :...
).
Availability of the Official DPX Standard
Availability in Single Copy:DPX is defined in SMPTE standard number 268M-2003, available in their store.
With Other SMPTE Standards:
SMPTE's website also has information about the ordering of CD-ROMs, which contains SMPTE standards including the SMPTE 268M-2003 standard.
See also
- Digital intermediateDigital intermediateDigital intermediate is a motion picture finishing process which classically involves digitizing a motion picture and manipulating the color and other image characteristics. It often replaces or augments the photochemical timing process and is usually the final creative adjustment to a movie...
- Display resolutionDisplay resolutionThe display resolution of a digital television or display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by all different factors in cathode ray tube , flat panel or projection...
- Film-outFilm-outFilm-out is the process in the computer graphics, video production and filmmaking disciplines of transferring images or animation from videotape or digital files to a traditional film print...
- Film recorderFilm recorderA Film Recorder is a graphical output device for transferring digital images to photographic film.All film recorders typically work in the same manner. The image is fed from a host computer as a raster stream over a digital interface...
- post production
- digital film
- TelecineTelecineTelecine is transferring motion picture film into video and is performed in a color suite. The term is also used to refer to the equipment used in the post-production process....
- DJV Imaging
External links
- http://www.cineon.com/ff_draft.php
- http://www.smpte.org/
- http://www.imagemagick.org/script/motion-picture.php
- SMPTE DPX v2 Image Format reader/writer C++ library