[raphlinus]

If I were writing it, I might start with a physical interpretation of alpha as a blend of transmission and reflection of light (it basically does this) but emphasizing that has to be actual luminance, which RGB isn't. I'm not even sure I'd add a whole lot of content as rearrange it so the role of linearity in blending was closer to the top.

[iamdead]

My hot take is that physical correctness for graphics is very much in vogue right now, but this is coming at the sacrifice of psychovisual and physiological properties of graphics.

Gamma-correct compositing is one of those things that is actually quite difficult to detect, by most viewers, in most situations. For that reason it does not deserve to be put at the top.

[Matumio]

Compositing may be hard to judge, but crappy gamma-incorrect zoom (same problem) is visible everywhere.

Did you ever notice how the brightness of a zoomed-out photographs suddenly changes? Look for images with fine high-contrast structures, like brightly lit branches or distant fences. For example https://en.wikipedia.org/wiki/Crown_(botany) - see how the picture gets brighter as it de-blurs? This is not intentional. More often a region is just a bit too dark.

Same with thin line art. Zoomed-out cross-hatching is the worst-case. When you do inking on a PC you may only work zoomed-out, so you can print later in much higher resolution. Once you look at the print, the emphasis is all wrong. Some lines disappear while others are much too strong. You are about to complain to the printer but zoom in to check and notice that the print was flawless.

Some older programs (e.g. feh) switch to nearest-neighbour interpolation while you are panning. This looks crappy but actually gives you the correct average brightness (because it doesn't do any color compositing). You can see the brightness jump back to incorrect values when panning stops.