The Cineon file format was designed specifically to represent scanned film images, and it
has some interesting differences from other formats such as tiff and Jpeg:
- The data was stored in log format, directly corresponding to the negative density,
density = log(exposure).
- Each channel (R,G,B) was 10 bits, packed 3 per 32bit word, with two bits unused.
- The format had a notion of the "black point" and "white point", conventionally 85 and 685 on the 0-1023 scale (but adjustable). Pixel values above 685 are "brigher than white", such as the sun, chrome highlights, etc. This is the HDRI concept, and in fact this concept was used in the film industry for several years before it came to be called HDRI through Debevec's work later in the 1990s.
The Cineon format was defined in a Kodak document by Glen Kennel, Conversion of 10bit Log
Film data to 8bit Linear or Video Data. The format has been replaced by a related format called DPX.
