Exposure With Highlights Desaturation


https://forum.reallusion.com/Topic429683.aspx
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By GOETZIWOOD STUDIOS - Last Year
Hi,

In the same spirit of the "Exposure With False Colors" post and if you have watched the video "The Secret Ingredient to Photorealism", you should now understand that it is important to get that desaturation effect in the highlighted parts of your images to avoid unnatural over saturation and color shifting as we see too often in iClone rendered images. That is, if like me, you are after PBRish / plausible realistic renderings.

There is a way to simulate that in iClone even if there is no Tone Mapping, by creating a special LUT that you can use in the Visual -> Effect -> Post-Effect section of iClone.
You will find attached to this post a iEffect (that already contains the False_Color LUT) with the Highlight_Desaturation LUT. I created it with a pretty violent effect so you can reduce it by using the "Effect Contribution" parameter slider. You can also create your own LUT with a different "ramp", I encourage you to experiment.

The results are pretty interresting. Here without desaturation:
https://forum.reallusion.com/uploads/images/881d9cae-b4b3-458c-b803-cd84.png

Here with full desaturation:https://forum.reallusion.com/uploads/images/49ddadab-6652-4d9c-8247-5915.png

Indeed, it feels more natural to me.

Note that in the iEffect I've set the Highlight_Desaturation LUT before the False_Color one because when you desaturate a color a burnt color channel may get a lower value and then not be burnt after being desaturated, and you must see that with the false colors in order to properly adjust your exposure.
By GOETZIWOOD STUDIOS - Last Year
Note: I've also included the Color_Adjust effect in the iEffect because with the "Contrast" slider you can adjust like a gamma effect, which means your image will be more or less "bright" but without affecting to much your extreme dark and highlight values (up to a point that is). And you can do it safely thanks to the False_Color LUT. Remember though, don't exaggerate the effect because it act on the rendered image, not on the actual scene lighting, you may end up with artefacts if you do so. 
By GOETZIWOOD STUDIOS - Last Year
@Nathan
You are very welcome Nathan. Thank you Wink
By ultimativity - Last Year
@GOETZIWOOD STUDIOS

Thanks so much for posting your LUT. I watched the same tutorial for Blender, but have not experimented with LUTs in iClone.  What I like about your post is using the LUT to solve a specific problem. This makes LUTs much less daunting for me.
Thanks again,
Nathan