Halfway between black and white is not
always the gray you expect.
In a typical image, stored color values
are encoded for display.
Averaging those values can give a darker
result than averaging the underlying
light.
That difference matters when you blur an
image, blend layers, or build a glow.
A transition can look muddy even when the
arithmetic seems correct.
The fix starts before the effect.
Convert color into a linear working space,
perform the calculation there, then
transform the result for display.
Keep data maps, like roughness and
normals, separate from color textures;
they represent instructions, not
photographed light.
Color management cannot rescue every
artistic choice.
But it gives your tools a consistent
foundation,
so you can judge the image instead of
fighting a hidden math problem.