ACEScg colorChecker 0.191

To help me understand ACES further I downloaded the ACEScg ColorCheker2014 EXR from github. However I soon became stumped on something very simple. I was under the impression that the mid gray color swatch on the colorChecker was 18% percent, however when I pick over this swatch it gives me the value r:0.19031 g:0.1903080 b:0.198994. Shouldn’t it be 0.18?

Sorry in advance for this question.


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Hi @adamodonnell,

This is the correct colour indeed, it is not perfectly neutral because it is pretty much impossible to produce paints that are neutral across the entire visible spectrum. It is not equal to 18% because it is not meant to be :slight_smile: It is a mistake a ton of people commonly do when thinking that the Neutral 0.5d patch is meant to be 18%. It is not a 18% gray card:

Now, whether it matters depends how much precise you want to be, more often than never it is good enough especially for creative applications, however, if you are performing precise calibration, it is obviously super important.




Thanks Thomas, really appreciate your time and knowledge.


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