Hi J Meyer,
I was about to post a question on this topic today myself, though I was using bitmaps for color purposes, not SSS or displacement. Perhaps someone can answer the combined topic question:
If you add color (from powerfractals, grayscale bitmaps, etc.) it appears that the final color can be above white. This would make sense if TG2 allows greater than 1 values for grayscale, and hence there is a clamp function.
However, is it the default processing of TG2 to allow over 1 (pure white) if you add color together? For example, Photoshop does not do this, but automatically clamps at 1 (pure white) unless you're using 32-bit images.
In the situation when the "over-1 white" appeared, I was adding two 8-bit grayscale bitmaps together, not 32-bit.
When I added two grayscale bitmaps together, the overlapping white areas turned "whiter" than white. Was this over-1 white value considered to be luminous then?
It was necessary to add a "Clamp 0 1 Color" node after the Add Color node. Then the white bitmap added to the white bitmap stayed at white. I'm just wondering if adding a "Clamp 01 color" node should be the standard workflow or if this was a unique case.
Similarly, if I subtract color (black minus black) or multiply color from grayscale bitmaps, should I also be using a Clamp 01 Color node? I noticed the above-white issue because it looked luminous, but I'm not sure if a "darker-than-black" color would be blatantly visible yet may still mess up certain functions.
I'm primarily asking this when using grayscale bitmaps as Blender shaders.
Thanks,
-Matt