LCh Lightness value L=54.3 in range 0..100 too light for pure red (255,0,0)
Environment/Versions
- GIMP version:2.10.18, 2.10.30
- Package: apt (2.10.18), flatpak (2.10.30)
- Operating System: Linux, Ubuntu
Description of the bug
It seems that the LCh lightness/luminance value for pure red, i.e. L=54.3, belongs to a range of 0 to 255 for the lightness/luminance. But any colour picker uses a range of 0 to 100 for LCh lightness. So a value of L=54.3 is too light for pure red. This issue also occurs when desaturating a pure red by luminance. The resulting gray is too light for pure red, i.e. it produces more than 50% gray for pure red. When using the luminance formula for rgb values, I calculate a value around L=22 for pure red, not L=54.3. Also this is visible when using the LCh layer modes Color and Chroma. A desaturated red layer is too light. Probably I confused some color space or gamma correction settings, since I am definitely no expert in color space theory?
Reproduction
Is the bug reproducible? Always
Reproduction steps:
- Choose a pure red (R=255, G=0, B=0)
- LCh shows for the lightness L=54.3, but with respect to the range of 0 to 100.
Expected result: A value of around L=22 for pure red, i.e. a quite dark lightness/luminance for pure red.
Actual result: A value of L=54.3 for pure red, which is to light when a range of 0 to 100 is used for the lightness.