Reference¶
About Color Spaces¶
The standardized OpenFX [1] plugin interface used by Colour Look and Feel does not explicitly provide information or facilities to obtain the particular RGB color space passed onto the plugins. The standard only specifies that the RGB data is linear but no further tone curves are specified.
As such Colour Look and Feel allows nodes to accept XYZ as well as RGB data of varying color spaces for their inputs and outputs. This input and output color space can be selected for each node individually and is set to sRGB by default.
Color Space Transformation Pipeline¶
Color space transformation pipeline used in Colour Look and Feel.¶
The above shows the color transformation pipeline used internally in the nodes. An arbitrary input image is passed in, if the source color space has a non-linear encoding the OETF function will be used to remove the non-linear component, subsequently a linear transformation is applied to convert the image to an unified internal color space. After the node action is applied the process is reversed by linearily transforming the color space back into the source color space followed by encoding non-linear aspects.
See Color Component Transfer Functions (CCTF) for more on the OETF/EOTF functions.
Note
Some compositing software’s may already implicitly convert the input image to an unified node color space. In this case use the default XYZ color space.
Color Component Transfer Functions (CCTF)¶
Color Component Transfer Functions (CCTF), also known as Electro-Optical Transfer Functions (EOTF) or Opto-Electronic Transfer Functions (OETF), are essential in video and imaging systems for mapping color values between linear light and non-linear signal domains. They optimize storage and transmission by aligning with human perception, which is more sensitive to darker tones. During encoding, the OETF converts linear light to non-linear signals, and during decoding, the EOTF reverses this process. Proper use of CCTFs ensures accurate brightness and color reproduction, maintaining image quality.
CCTF functions as such allow the application of non-linear color space transformation components. For linear color spaces CCTF functions are not implemented and as such will not provide any effect.
Available Color Spaces¶
The following color spaces are currently available to be selected for node input and output data:
Name |
Description |
CCTF |
|---|---|---|
XYZ |
CIE 1931 XYZ |
No |
sRGB |
Standard sRGB |
Yes |
Rec. 702 |
ITU-R BT.709-6 |
Yes |
Rec. 2020 |
ITU-R BT.2020 |
Yes |
ACES2065-1 |
ST2065-1 |
No |
ACEScg |
ACES Comp. |
No |
ACEScc |
ACES Col. Corr. |
Yes |
ACEScct |
ACES Col. Corr. |
Yes |
The CCTF field refers to whether the color space has an associated CCTF function, if not the Apply OETF and Apply EOTF functions do nothing.
Common White Point Selection Parameters¶
White points can be defined using one of multiple methods in all of the nodes of Colour Look and Feel. The following methods are available.
- Illuminant
Select a white point using a standard illuminant. Currently supports most standard CIE illuminants, see Illuminants for further detail.
- Color
Select a white point using a color value.
- Tristimulus
Select a white point using a tristimulus value xy. This can be used to specify non-standard illuminants.
- CCT
Select a white point using a Correlated Color Temperature (CCT) in degrees Kelvin. This approximates the white point using a black body temperature formula.
The selected white point is handled independently of the node color space.
Illuminants¶
The following illuminants are available with their CIE 1931 2 degree standard observer tristimulus values.
Standard |
Name |
CCT |
|---|---|---|
CIE 15:2004 |
CIE A |
2856K |
CIE B |
4874K |
|
CIE 15:2004 |
CIE C |
6774K |
CIE 15:2004 |
CIE D50 |
5003K |
CIE 15:2004 |
CIE D55 |
5503K |
CIE 15:2004 |
CIE D65 |
6504K |
CIE 15:2004 |
CIE D75 |
7504K |
CIE D93 |
9305K |
|
CIE E |
5454K |
|
CIE 15:2004 |
CIE F1 |
6430K |
CIE 15:2004 |
CIE F2 |
4230K |
CIE 15:2004 |
CIE F3 |
3450K |
CIE 15:2004 |
CIE F3.1 |
2932K |
CIE 15:2004 |
CIE F3.2 |
3965K |
CIE 15:2004 |
CIE F3.3 |
6280K |
CIE 15:2004 |
CIE F3.4 |
2904K |
CIE 15:2004 |
CIE F3.5 |
4086K |
CIE 15:2004 |
CIE F3.6 |
4894K |
CIE 15:2004 |
CIE F3.7 |
2979K |
CIE 15:2004 |
CIE F3.8 |
4006K |
CIE 15:2004 |
CIE F3.9 |
4853K |
CIE 15:2004 |
CIE F3.10 |
5000K |
CIE 15:2004 |
CIE F3.11 |
5854K |
CIE 15:2004 |
CIE F3.12 |
2984K |
CIE 15:2004 |
CIE F3.13 |
3896K |
CIE 15:2004 |
CIE F3.14 |
5045K |
CIE 15:2004 |
CIE F3.15 |
6509K |
CIE 15:2004 |
CIE F4 |
2940K |
CIE 15:2004 |
CIE F5 |
6350K |
CIE 15:2004 |
CIE F6 |
4150K |
CIE 15:2004 |
CIE F7 |
6500K |
CIE 15:2004 |
CIE F8 |
5000K |
CIE 15:2004 |
CIE F9 |
4150K |
CIE 15:2004 |
CIE F10 |
5000K |
CIE 15:2004 |
CIE F11 |
4000K |
CIE 15:2004 |
CIE F12 |
3000K |
CIE 15:2004 |
CIE HP1 |
1959K |
CIE 15:2004 |
CIE HP2 |
2506K |
CIE 15:2004 |
CIE HP3 |
3144K |
CIE 15:2004 |
CIE HP4 |
4002K |
CIE 15:2004 |
CIE HP5 |
4039K |
CIE 15:2018 |
CIE LED-B1 |
2733K |
CIE 15:2018 |
CIE LED-B2 |
2998K |
CIE 15:2018 |
CIE LED-B3 |
4103K |
CIE 15:2018 |
CIE LED-B4 |
5109K |
CIE 15:2018 |
CIE LED-B5 |
6598K |
CIE 15:2018 |
CIE LED-BH1 |
2851K |
CIE 15:2018 |
CIE LED-RGB1 |
2840K |
CIE 15:2018 |
CIE LED-V1 |
2724K |
CIE 15:2018 |
CIE LED-V2 |
4070K |