High light fix and premature desaturate

Discussions - Using ACES Video Games
21

Hello, just wanted to share this link : Simon's Tech Blog: DXR Path Tracer
that shows a similar “fix” about blue highlights.

I think this is a good opportunity to re-emphasize Nick’s answer :

The “blue highlight fix” LMT is not really intended to counter the hue skews at high exposure, but rather the very harsh artefacts resulting from values which are outside the AP1 gamut. Because you are starting with an sRGB colour, it is well within AP1, so that LMT is not really an appropriate fix.

Thanks,
Chris

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22

There’s always a way to take sRGB blue and bring it outside of the AP1 gamut :slight_smile: The easiest one is using a gamut expansion operator (from linear sRGB to AP0) where higher luminance pixels are expanded more than lower luminance ones as an IDT. Add heavy grading on top and you have a recipe for negative values.

Cheers,
Jean-Michel

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