Digital Picture Exchange
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|Type of format||Image file formats|
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 clarify information stored (and storable) within each file.
The DPX file format was originally derived from the Kodak Cineon open file format (
.cin file extension) used for digital images generated by Kodak's original film scanner. The original DPX (version 1.0) specifications are part of SMPTE 268M-1994). The specification was later improved and its latest version (2.0) is published by SMPTE as ANSI/SMPTE 268M-2003.
Metadata and Standard Flexibility
SMPTE Specifications dictate a mild number of compulsory metadata, like image resolution, color space 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).
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 Standards Digital Library Subscriptions, which contains SMPTE standards including the SMPTE 268M-2003 standard.
- Digital intermediate
- Display resolution
- Film recorder
- post production
- digital film
- SMPTE DPX v2 Image Format reader/writer C++ library