Why use "don't affect colors" when you lose all color mapping control?

V-Ray for 3ds Max V-Ray for 3ds Max :: General
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So to do this, using a workflow where Dont affect colours is unticked is the only way, right?
Yes, this is correct. When “Don’t affect colors” option is used the Bright /Dark multiplier and Gamma values are only taken into account for the sampling calculation not for the final rendering.

A) Vray Color Mapping - Linear Multiply, Gamma 1, Dont affect colors un-ticked, SRGB on in VFB, exr files saved through VFB.

So from what I’ve read, this burns in the color mapping to the images.
Yes, with this approach you can control the Bright and Dark multipliers and they will be burned into the exr.
The sRGB option will only preview the output with sRGB curve applied.

The alternative to stop color being burned in is to use these settings -

B) Vray Color Mapping - Linear Multiply, Gamma 2.2, Dont affect colors ticked, SRGB on in VFB, exr files saved through VFB.
Yes, that is correct.

Both images render the same as in terms of colour and passes, so I’m slightly confused as to the differences with color mapping.
instinct explain very well why you get different outputs with those two approaches. Generally with the second one V-Ray samples much brighter scene (because of the 2.2 gamma) compare to the first approach. Therefore both images get different noise level and rendering times. But they both get the same output because of the " Don’t affect colors" option.

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Dean…sorry about that, yes, if you are saving out as an exr, you would have to change the gamma to 1.0. I now pretty much save out to 16bit Tiff’s where I can use the settings I described above. There’s enough information for my use in a 16bit image. EXR’s are large and I have not found an advantage to having all of that information in my still image. 16bit works just fine for my needs and workflow.

Back to EXR’s…Having changed the gamma to 1.0, you could un-tick “dont affect colors” and tick sRGB in th VFB and get the correct output in both
the frame buffer and photoshop. This method gives the advantage of having the options to change color mapping types and settings, but you give up in the improved sampling. Your question regarding adjusting "noise threshold’ seems
valid.

I prefer to keep things simple and save as a 16bit tiff, where I can set gamma to 2.2, un-check “don’t affect color”, un-tick “sRGB” and my output is correct. I keep all of my
color mapping options alive. I am not convinced that ticking “don’t affect color” and giving up on color mapping options is the better of the 2 workflows.

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Don’t affect colors is meant for linear workflow. And with linear workflow you save linear without color mapping hence you do not need that. Burning in color mapping does not really make sense in that context. The idea is to sample properly, and save linear and everything else is post. If you save to tif. Nevermind i’d say.

Regards,
Thorsten