Cineon
From Wikipedia, the free encyclopedia
Cineon was the first computer system designed by Kodak for digital intermediate film production. It included a scanner, tape drives, workstations with digital compositing software, and a film recorder. The system was first released in 1993 and was abandoned by 1997. As an end-to-end solution for 2K and 4K digital film production, the system was well ahead of its time. The major components of the system (scanner, workstation software, and recorder) have all received AMPAS Scientific and Technical Awards.
Although the compositing software itself no longer is sold, the file format that it defined to store images continues to exist and is in common usage in the film visual effects world.
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[edit] Cineon file format
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.
[edit] Documentation
Conversions to the Cineon format were defined in a Kodak document by Glenn Kennel, "Conversion of 10bit Log Film data to 8bit Linear or Video Data".
SMPTE standardized the format further into a related format called DPX which can store more varieties of image information as well as additional header information.
[edit] History
In 1993 Snow White and the Seven Dwarfs became the first film to be entirely scanned to digital files, manipulated, and recorded back to film. The restoration project was done entirely at 4K resolution and 10-bit color depth using the Cineon system to digitally remove dirt and scratches and restore faded colors.
[edit] Cineon AIM Calibration
For a digital film system to operate correctly with Cineon 10-bit aims, the following calibration is desired mapping code values to StatusM densities. These are in the form of the AIM for a film recorder (where the Dmin should be adjusted based upon what the real lab creates on its '42 negative.
| Reference Code Values | StatusM ( above b+f ) | |||||
|---|---|---|---|---|---|---|
| Cineon Ref Black | 95 | 95 | 95 | 0.193 | 0.188 | 0.158 |
| Cineon Digital LAD | 445 | 445 | 445 | 0.871 | 0.932 | 0.915 |
| Cineon Ref White | 685 | 685 | 685 | 1.336 | 1.442 | 1.434 |
| Peak White | 1023 | 1023 | 1023 | 1.991 | 2.160 | 2.165 |
