CIN (Cineon, .cin)
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 pixel data represents "printing density", the density that is seen by the print film. Thus, Cineon files are assumed to operate as part of a reproduction chain keeping whatever values are originally scanned from a negative or positive film. Since a system gamma of 1.0 is preserved, any negative can be reproduced on the recorder retaining the original neg's gamma. The original calculations to determine the conversion from real densities to printing densities was based upon 5244 intermediate film. Conversion of Cineon Printing Density (CPD) to statusM can be achieved with a 3x3 matrix or by using tables contained in the Kodak 'Digital LAD' document. This document shows a specific relation between Cineon Code values and StatusM densities.
The data is stored in log format, directly corresponding to density of the original negative. Since the scanned material is likely a negative, the data can be said to be "log with a gamma".
To evaluate original scene luminances from Cineon data, the camera negative should have been developed with a sensitometric strip so that the actual developing gamma can be determined. The film can be unbuilt by using the unique per layer contrasts of the color negative.
Each channel (R,G,B) is 10 bits, packed 3 per 32bit word, with two bits unused.
The format has a notion of the "black point" and "white point" used for conversion to more limited range video signals. Conventionally, these points are 95 and 685 on the 0-1023 scale (but should be adjusted based upon actual negative content).
Pixel values above 685 are "brigher than white", such as the sun, chrome highlights, etc. The concept of a 'soft clip' was introduced to make the rolloff of whites more natural. Pixel values below 95 represent black values exposed on the negative (the clear base of the film). These values can descend in practice as low as pixel values 20 or 30.
