ASC CDL
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The American Society of Cinematographers Color Decision List (ASC CDL) is a format for the exchange of basic primary color grading information between equipment and software from different manufacturers. The format defines the math for three functions: slope, offset and power. Each function uses a number for the red, green, and blue color channels for a total of nine numbers comprising a single color decision. A tenth number for saturation has been proposed but not yet standardized.
The ASC CDL was developed by the ASC Technology Committee, a combined group of cinematographers, post-production engineers, and other motion picture industry professionals.
The CDL allows color corrections made with one device at one location to be applied or modified by other devices elsewhere. For example a cinematographer filmling on location can create a color correction with a small portable device, sending the CDL to a colorist in post-production to use as a starting point for final color correction. Although the basic controls of most color correction systems are similar, they differ slightly in implementation and data storage. The ASC CDL is a common standard that color correctors can translate their proprietary settings to and from.
The ASC has defined an XML schema for exchanging CDL data, along with other metadata about what image(s) the color corrections were applied to, the type of input signal used, and the viewing device and environment. They have also standardized methods for using CDL data withing the following file formats:
- Avid Log Exchange (ALE)
- Film Log EDL Exhange (FLEx)
- CMX Edit Decision List
Combined Function
The formula for ASC CDL color correction is:
where
- is the color graded pixel code value
- is the input pixel code value (0=black, 1=white)
- is slope (any number 0 or greater, nominal value is 1.0)
- is offset (any number, nominal value is 0)
- is power (any number greater than 0, nominal value is 1.0)
The formula is applied to the three color values for each pixel using the corresponding slope, offset, and power numbers for each color channel.
Some systems supporting ASC CDL
- Autodesk finishing, VFX and colour grading systems
- Avid editing systems
- da Vinci Systems Resolve and 2K Plus color correctors
- Digital Vision Film Master color corrector
- FilmLight Baselight color correction system
- Gamma and Density 3cP on-set color correction system
- IRIDAS SpeedGrade color corrector
- Pandora Revolution color corrector
- Synthetic Aperture Color Finesse
- The Pixel Farm PFClean Film Restoration Software and Systems
- Thomson Grass Valley BONES Dailies
- Workflowers WF_x plugins for color correctors