DPX / Cineon
DPX, the short form of Digital Picture Exchange, is a common file format for digital film work and is an ANSI/SMPTE standard (268M-2003). The file format primarily represents the Optical density of each color channel of a scanned negative in a 10-bit log format where the Gamma correction of the original camera negative is preserved as taken by a film scanner. DPX provides a great deal of flexibility in storing color and other information for exchange between production facilities. Multiple forms of packing and alignment are possible.
The DPX file format is derived from the output file format of the Kodak Cineon film scanner, and has been published by SMPTE as ANSI/SMPTE 268M-2003 (originally was version 1 268M-1994).
Availability of the Official DPX Standard
Availability in Single Copy:
SMPTE has the DPX standard 268M-2003  (April, 2007)
GraphicsMagick has implemented the format, info available 
Cineon Image File Format Draft (both SDPX and the Cineon 4.5 draft) 
4.5 Draft - Image File Format Proposal for Digital Pictures (November, 1990, PDF)