The following is an overview of the stock colour space choices in the Autodesk colour transform collection. (You may also use your own LUTs via creating User Colour Spaces.)
Background info: "Gamma and Gamut"
Many of the colour spaces use a "Gamma / Gamut" naming convention, for example, "gamma 2.4 / Rec.709". The "Gamma" describes the relationship between the encoded values and linear values. The "Gamut" specifies the colour primaries used.
- The term "Gamma" is used very loosely since many of the colour spaces use a logarithmic function rather than a power law.
- Some colour spaces say "(no primaries)" for the "Gamut". This means that the transform to the working colour space is only a 1d-LUT -- there is no adjustment for primaries. One way of interpreting this is that the source values use whatever primaries the selected working space does.
- There are pros and cons of correcting for Gamut (that is, accounting for differences in the primaries between capture, working space, and output). One disadvantage is that it can create negative values. One of the advantages is that you can convert various sources into a common working space with a gamut that is as large or larger than any of the intended deliverables.
- When you don't want to correct for Gamut, use transforms that primarily all use the same Gamut values. Choose the Gamma based on the actual encodings.
Broadcast and Displays options
- The Broadcast category contains the conventional video colour spaces. For the Gamma (EOTF), all the SDR options use ITU-R BT.1886 (essentially a 2.4 gamma).
- The Rec.2100 options are for HDR monitors.
- The Display category has the other video-like colour spaces.
- sRGB, AdobeRGB, and ProPhotoRGB are often used for tagging images from Photoshop, etc.
- DCDM is the space used for digital cinema distribution masters: X'Y'Z' (which is related to CIE-XYZ but with a gamma 2.6 non-linear encoding).
- DCI-P3 is the gamut for the SMPTE Reference Projector and is widely used in grading theaters.
- The Eizo and HP options are for high-end monitors in their Native mode.
- The ST-2084 (PQ) options are for HDR monitors.
- These colour spaces are all in the Video family.
Camera options
- Includes ARRI, Canon, Panasonic, RED, Sony, VisionResearch, and generic ITU OETFs.
- Mostly uses Gamma / Gamut naming
- The "(safeBlack)" option applies a slight toe in the response curve to avoid negative values.
- These options are in the Log or Scene-linear families.
Log options
- ACEScc and ACEScct logarithmic working spaces for colour correction. ACEScct has a slight toe in the shadows to make for easier grading.
- ADX10 is useful for typical Cineon-style film scans. ADX16 is a wider range encoding capable of handling more recent film stocks.
- Lots of Gamma / Gamut colour spaces useful when not wanting to correct for Gamut.
- Two standard Log-to-Lin curves provided: Cineon is the classic 95/685/0.6 curve (be careful since values below 95 become negative); JZP is the Josh Pines (aka "pivoted") curve which is similar except 445 maps to 0.18 and all log values map to positive linear values.
- These options are in the Log family.
Scene-linear options
- All are scene-linear colour spaces, the only difference is the Gamut (primaries).
- ACEScg is a recommended space for CGI and compositing with a gamut that is wide, but not too wide.
- These options are in the Scene-linear family.
Textures options
- Large set of various Gamma / Gamut combinations.
- Intended for Texture or "Linear" Workflows where the intention is that a gamma-corrected value of 1.0 maps to a scene-linear value of 1.0.
- These options are in the Video family.
Data options
- The options in the Data category are to tag Mattes, Normals, Z-Depth, AOVs, etc.
- This can be useful to assign a viewing transform appropriate for the type of data (e.g. since Normals are half negative, it can shift everything up; for Z-Depth it could compress the range logarithmically).
- Keyer outputs are tagged as Matte.
- Action outputs use many of the other Data options.
- These options are in the Data family.
View Transform options
Two Viewing Transform options deserve special discussion: "Video (colorimetric)" and "Linear (gamma-corrected)". The goal of these two transforms is to take advantage of the Graphics Monitor and Broadcast Monitor colour space settings to simply present an accurate 1:1 display of the source colours on the given hardware. These transforms essentially represent an identity View Transform that does no "picture rendering" for display. They are very similar except the former expects as input a colour space in the Video family and the latter expects as input a colour space in the Scene-linear or Log families.
Here are some more notes on the View Transforms options:
- View Transforms convert from a scene-linear colour space to a video colour space. Using the terminology from ITU-R BT.2100, this is an OOTF (Opto-Optical Transfer Function).
- The ACES Output options essentially calculate a custom RRT+ODT for the given display. The choices are for the dynamic range, viewing conditions, and desired white point options supported in the ACES 1.0 system.
- The Cameras category has renderings for common digital cinema cameras.
- The Diagnostic category has options for camera-style exposure metering, flagging out-of-range values, etc.
- The Legacy category has traditional simple Gamma curves that do not apply any correction for Gamut.
- The Rec.2100 and Rec.709 options are various OOTFs from the standards.
Miscellaneous options
- "From File or Rules" first tries looking at the file header, then applying the Input Rules
- "From Project" uses the default project Working Space
- "From Source" uses the incoming colour space
- "Raw" never applies any conversion. Essentially the source values are just retagged as whatever the Working Space is set to.
- "Unknown" is used for Archive restores and Wire transfers from older projects. It essentially means "not tagged yet".
- "+Add New" allows you to create a User-defined Colour Space.