[krackers]

Sure but modern ICC color-managed workflows (e.g. digital photography, printing) basically don't distinguish between EOTF and OETF. Assuming your source is tagged correctly and all displays have a profile matching their true response, you necessarily need to linearize with the inverse of the encoding gamma. All edits are done directly in the source color space, if the viewer's profile differs from the source it's up the viewer to translate accordingly. You don't edit images "on the assumption" that they'll be decoded with a 2.2 gamma.

For some reason video workflows never adapted to the ICC system (probably because in CRT days you couldn't really adapt your decode gamma on the fly) which is basically where the whole debate in https://gitlab.freedesktop.org/wayland/wayland-protocols/-/m... comes from.

I'm not saying that the people using 2.2 EOTF are wrong, but all this just adds to the absurdity: in the modern day where LUTs are cheap and plentiful, instead of tagging content as an ambiguous sRGB it could simply be tagged as gamma 2.2 if it's actually intended to be decoded at that gamma.

[anikom15]

It depends what you want to apply your linear functions on. If you want to work directly in the source scene light (e.g. photography), then it would make sense to use the inverse OETF. If you are blending graded scenes of emissive light, i.e. a movie, then using the EOTF makes sense. The reason for this is that movies are graded with that EOTF in mind, so by linearizing with that EOTF, you get a resulting linear value as it is intended to be seen by a viewer.

Regardless of what you use for a linearizing function, the more important thing is that you use the correct encoding function afterward, so that you don’t introduce any additional gamma correction. For example, it was common to use a simple squaring function for speed. This gives fairly good results as long as you apply the square root function afterward to restore the original gamma correction. It doesn’t matter if the source is 2.2 or 2.4 gamma encoded or something else, that correction will be preserved. The blending post-linearization will be less accurate, but much better than not linearizing at all.

[krackers]

>The reason for this is that movies are graded with that EOTF in mind, so by linearizing with that EOTF

I guess this is the part I find anachronistic. Why do we work in the source scene light for photography, but do the opposite for videos? It makes sense if you assume the viewing device is "dumb" (like a television or CRT, especially in the analog days) but by now I assume the workflows are all fully digital, and even the most basic output device can apply LUTs. When digital video container formats were introduced, why didn't they align with what ICC did? It would have saved a lot of headache for everyone, compared to limited NCLC tags and the mess around EOTFs.

[anikom15]

It’s because the viewing format has a fairly consistent gamma curve relative to viewing environment ambient light level. In a theater its about 2.6 and this works with no ambient light, and in a living room its about 2.4 with dim lighting, and on a computer screen its about 2.2 with typical office lighting. With controlled lighting, the perception of the output image under these three different gammas will be identical. This gives graders a great deal of precision. They can calibrate their screen and studio to appear exactly as it should to these idealized environments. That a number of people watch content in non-ideal environments is irrelevant (even though its often brought up as a strawman argument against consistent working environment viewing conditions).

With photography, you don’t have that control at all because traditionally photography was about prints. Every printer (regardless of kind) had to be profiled and you needed an explicit ICC conversion process for it to work. If you are solely publishing photographs digitally and have no intention of printing, you actually could adopt a film workflow and it would be just fine.

In short, film production doesn’t actually need the added complexity of ICC profiling. They could adopt it, but it’s not strictly necessary. Trouble comes when people don’t understand the fundamental reason why gamma correction and different primary spaces exist in the first place.