different results between filters adjustments and develop adjustments

[fix38]

I could figure out that making some adjustements in graduated filter (set outside of the picture so that it would cover the whole picture with 100% opacity) does NOT produce the same result as setting things in the develop module which is very annoying (maybe a bug ?)

my guess is that setting highlights to +40, Shadows to -40, whites to +15 and blacks to -15 should lead to same results as having all sliders to 0 in dev module but setting the same adjustements in the described graduated filter.
which is obviously not the case.Is there some kind "relationship" between those ?
Best regards !

[richardplondon · Accepted solution]

These two methods will not necessarily get the same results, partly because they are doing different things. They can't necessarily balance each other out exactly.

For example: say that I set some [+] tone adjustments in my Basic panel, enough to blow some highlights. I can apply some [-] tone local adjustments (for example in a "grad filter") to compensate, and doing that will bring back these highlights.

If instead, I had started with [+] tone adjustments in my grad filter, which blow out the highlights: I might try to rescue these highlights with [-] tone settings in my Basic panel. But that might not work - even though the magnitude of these adjustments was identical to those in the first example. My Basic panel adjustments might be occurring on top of some pre-processing settings which had in effect "already" blown the highlights from the source picture data, beyond retrieval.

The local adjustments get applied FIRST onto the source image (making it darker, say) and only THEN are the Basic panel adjustments applied. One sort can't cancel out or combine with the other sort directly; processing happens cumulatively according to a fixed internal sequence (which the user cannot change; but which it is helpful to understand).

Of course it's more convenient that Adobe names these sliders in the Local adjustments the same as the corresponding Global ones, since they are similar. But they are not fully interchangeable, and their numbers don't necessarily ACHIEVE the same thing always. Especially since some of these adjustments respond dynamically to whatever image content they encounter, rather than applying in a constant way regardless of that.