Unequal weighting between black and white in cycles; white has greater weight than black

Question

Using blender 2.92.0

I'm having an issue where the weight of the color white is greater than that of the color black when using nodes. It's hard to explain, so please check the images, I'll try to attach the blend file tomorrow.

See how the white band is significantly "thicker" than the black?

Both object are the same in every way except for that one has the order of the colors going into the mix shader flipped. I'm using a "mask" node I found online to get the behavior around the edges.

Here's what the node setup looks like:

I've tried to understand the issue on my own and believe it has to do with luminance; I understand that when a color node is connected to a factor node, blender uses the luminance value.... but that still doesn't really explain the disparity, since both setups are using the same mask and colors, just a different order of colors...

Answer 1

I see that you are used to working with gamma corrected colors or sRGB color model. It has some kind of symmetry - whites and blacks increase and decrease perceived brightness in the same speed.

But Blender uses linear colors - to imitate real world lightning. In real world and in linear colors, white has to add more energy to make it lighter than the black.

You might see this in color wheel in blender, then mid-gray actually 0.22 in linear color:

This is also the reason why you have to use non-color in normal maps.