Question about unbounded processing

Software darktable
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Thanks for the inputs here, in particular from @AD4K and @flannelhead, which confirms some muddled thoughts of mine – I’m now confused on a steadily higher level.

One question regarding the difference between scene- and display-referred: I’ve understood an important aspect of this to be that not only is the representation of luminance differences linear in scene-referred, but also that it is not bounded in computations. Since nobody mentions this, I wonder if one considers bounded representation to be inherent in non-linear representation – or have I misunderstood here?

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From my understanding the data in DT are processed in 32bit float so never bounded but if you use a module with a display referred UI then you can only modify data in that bounded 0-1 range… At least I believe someone told me this or I have messed it up… :slight_smile:

I believe I read something to that effect in here…

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I moved this over to a new thread, since it diverges from the original topic but deserves more attention even though it has been discussed before.

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The difference between scene-referred and display referred is in what the numbers mean.
In “scene-referred”, pixel values are proportional to light energy,
in “display-referred”, those values are proportional to log(light energy), which has (nasty) effects when you use blurs (as in most masking).

I don’t think there’s any reason why display-referred should be bound, that may just be an historical artifact: as a traditional display can’t receive values greater than 100%, the modules concerned weren’t really concerned with values outside the range (0…1). In programming, giving a display-referred module an input >1 would lead to “undefined behaviour” (i.e. anything can happen).

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It is not. Jzazbz color space / Jacob Rus | Observable is, for example, nonlinear and unbounded

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I learn something new. This is interesting and I will keep it in mind when masking.

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Is not a blur on the display’s linear light is good?

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I really have no idea what your question is…

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Glad I am not the only one…This is border line bot like… looking back over the few posts by this user they are mostly weird one line questions… sorry @slow if you are real…

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I am real. I mean it works good blurring on display linear light values? It is good to me?

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This can be tested objectively in newer versions of GIMP or other applications. I am sure there were several posts on this very question, but unfortunately, I cannot find it anywhere!

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I find this article by Elle Stone to be most definitive:

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You need to improve your English, as what you’re writing doesn’t make any sense. In the meantime, I suggest you use DeepL Translate: The world's most accurate translator

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Well, blurring the linear light coming out of the display will work (tracing paper is a good first choice).
That doesn’t help with editing the image though…

Honestly, I wouldn’t expect anyone using a name like “Leonard Jones” to need a translator to produce understandable english.