C4D Colorpicker : values and colorspace

[John_Do]

Hi,

I have some doubts about C4D colorpicker values and colorspace, especially after checking some values on Megascans albedo maps.

Nowadays it is well-known that a correct albedo value should be between 30/50 sRGB and 243 sRGB ( check Allegorithmic PBR guide or this chart if you want to know to dive into the subject ).

Until now I was happy with this kind of values, it seems right to me. The Corona diffuse linear level and RGB values match perfectly as expected and seems to confirm the theory.



Then after some questions to Juraj Talcik I had the idea to check RGB values on some Megascans albedo maps, like charcoal, dark concrete floor, black tiles, to get more reference points.



But these maps are really dark, with values between 5 and 20 sRGB. I'm really surprised by these low values, like if it should be loaded with a Linear profile. ( but no, I've checked the .json file and it means to be loaded with sRGB profile )

So I'm a bit confused and look for some definitive answer about the correct values and luminance on dark materials : which one is the right one ?

[maru]

I am not an expert on albedo / color profiles, so it's also sometimes confusing for me, but maybe these things will help you:
1) https://coronarenderer.freshdesk.com/support/solutions/articles/12000020988
2) https://forum.corona-renderer.com/index.php?topic=15792.msg99887#msg99887
3) https://forum.corona-renderer.com/index.php?topic=14123.msg91193#msg91193

[John_Do]

Thank you Maru, it helped a bit, but the gamma thing is somewhat hard to catch depending on the explanations. The tricky part ( at least for me ) is that gamma influences both numbers and color appearance, but both are sometimes mixed in softwares ( 2.2 numbers, 1.0 color, or the inverse ).

I did a cheat sheet to never be bothered again with this subject.

Some links :

- sRGB/XYZ/L*a*b*/CIELAB/ICCLAB/ITULAB
Color Space Conversion

- Gamma Encoding – Under the Hood

TL;DR: RGB/HSL color picker is in sRGB colorspace ( gamma space ), Corona level is in linear space.