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Filmic Tonemapper : why blue become pink (and not cyan) ?

Hey !

I just watch the Twitch on the filmic tonemapper and there is a small thing that bother me : why blue become pink with high exposure (or self ilum).

I tried the same test as Brian did in the video (take a high exposure photo of the screen) and I’ve got this result

We can see on the photo that the blue become cyan at high exposure.

So what happens in UE4 ? Is the pink color normal ?

Thx ! :wink:

Very nice comparison, I think we all agree that the pink looks wrong.

Mighty bump.

The issue is bad maths :wink:

Film cross talk. Film is made of layers and over exposure bleeds into other layers of the film. UE4 and your camera are handling it slightly differently, try the same test with several cameras and you’ll get a lot of variations in results.

I don’t think you will find any camera that will cause the blue to become anything else than cyan. I just tested it and got same results with camera like he got.

I did some tests, my explanation would only make sense if the film characteristic curve went blue, red, green, and most go blue, green, red, as far as I can tell.

I still think it might be related to how that film characteristic curve / film cross talk works in UE4.

You are correct. This is an issue with ACES and is a problem being tracked and worked on by the Academy. Here is the thread on the ACES forums discussing it Colour artefacts or breakup using ACES - #27 by Peter_Rixner - Post (DI, Edit, Mastering) - Community - ACESCentral. There is also a suggested fix there in the form of a matrix multiply. This effectively slightly tweaks the ACEScg primaries to get better results. We will see what the Academy decides to do as the official solution to the problem.

I could fix this by putting in the “enemy” color of whatever color you find looking “off”.

so i got my purple back to blue, and my orange back to red. (mostly… dont overkill on the strength…)