Digital Picture Exchange (DPX) is a common file format for digital intermediate and visual effects work and is an SMPTE standard (ST 268-1:2014). The file format is most commonly used to represent the density of each color 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 color information, colour spaces and color planes for exchange between production facilities. Multiple forms of packing and alignment are possible. The DPX specification allows 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 published by SMPTE as ANSI/SMPTE 268M-2003. Academy Density Exchange (ADX) support for the Academy Color Encoding System is added in the current version of the standard SMPTE ST 268-1:2014. Extensions for high-dynamic-range video and wide color gamut are standardized in SMPTE ST 268-2:2018.
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 the 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, they are left "empty". For example, Motion-Picture-specific metadata includes 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 includes full SMPTE time code, video overscan and field information, and signal/color level information.
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).
SMPTE ST 268-2:2018 defines a standards-based metadata section that supports Extensible Metadata Platform, XML, and KLV metadata representations.