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CMS

A color management system (CMS) describes how it translates the colors of images/videos from their current color space to the color space of the other devices, i.e. monitors. The basic problem is to be able to display the same colors in every device we use for editing and every device on which our work will be viewed. The color management operation consists of a color space conversion (matrix and 1DLUT). Colors that exceed the display's target color gamut are numerically clipped. Calibrating and keeping our hardware under control is feasible, but when viewed on the internet or DVD, etc. it will be impossible to maintain the same colors. The most we can hope for is that there are not too many or too bad alterations. But if the basis that we have set up is consistent, the alterations should be acceptable because they do not result from the sum of more issues at each step. There are two types of color management: Display referred (DRC) and Scene referred (SRC). Display-refered: 1.0f (white point) as the reference white level of the display. Scene-refered: 1.0f as the reference white of the used Color Space (nominal)

- DRC is based on having a calibrated monitor. What it displays is considered correct and becomes the basis of our color grading. The goal is that the colors of the final render will not change too much when displayed in other hardware/contexts. Be careful to make sure there is a color profile for each type of color space you choose for your monitor. If the work is to be viewed on the internet, be sure to set the monitor in sRGB with its color profile. If for HDTV we have to set the monitor in rec.709 with its color profile; for 4k in Rec 2020; for Cinema in DCP-P3; etc.
- SRC instead uses three steps:
  1. The input color space: whatever it is, it can be converted manually or automatically to a color space of your choice.
  2. The color space of the timeline: we can choose and set the color space on which to work.
  3. The color space of the output: we can choose the color space of the output (on other monitors or of the final rendering).
  ACES and OpenColorIO have an SRC workflow. Please note that the monitor must still be calibrated to avoid unwanted color shifts.
- There is also a third type of CMS: the one through the LUTs. In practice, the SRC workflow is followed through the appropriate 3D LUTs, instead of relying on the internal (automatic) management of the program. The LUT combined with the camera used to display it correctly in the timeline and the LUT for the final output. Using LUTs, however, always involves preparation, selection of the appropriate LUT and post-correction. Also, as they are fixed conversion tables, they can always result in clipping and banding.