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#1 2021-03-31 08:21:53

Bloke
Developer
From: Leeds, UK
Registered: 2006-01-29
Posts: 10,262
Website GitHub

Range for gamma correction

Just curious here. When adjusting gamma values, what’s a reasonable range (limit) to apply to either end? Brightness and contrast ranges go from 0 (no change) to -100 (none) to +100 (tonnes). But if I offer a similar scale for gamma, it’s ridiculous. I’m trying:

  • min: 0 (which pretty much makes the picture black)
  • max: 3 (which bleaches everything to the point you can barely see it)
  • step: 0.1 (for fine-grained control)
  • default: 1

Does that sound reasonable? Should we go higher? Not as far? Is there any point going all the way down to 0? Is the step between values okay? Affinity Photo seems to allow their range slider to go from 0 to 2 in thousandth increments, so maybe min=0, max=2, step=0.001 is better?

Thoughts?

Last edited by Bloke (2021-03-31 08:26:29)


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#2 2021-03-31 12:11:59

phiw13
Plugin Author
From: Japan
Registered: 2004-02-27
Posts: 2,347
Website

Re: Range for gamma correction

The Acorn 7 Gamma Adjust filter uses: min=0.25, max=4, step=0.01.

And it works the other way: “min” bleaches out while “max” darkens.

I don’t remember what other editors do, and actually never uses that filter except for some crazy playing, but completely out on the range of what people usually understand as image “correction”.


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#3 2021-03-31 12:18:23

Bloke
Developer
From: Leeds, UK
Registered: 2006-01-29
Posts: 10,262
Website GitHub

Re: Range for gamma correction

Thank you. Going all the way down to zero does seem a little pointless so maybe 0.25 is a decent lower bound. I’m trying 2 as an upper bound right now and it’s functional. Can’t see anyone using values much higher than this apart from special effects but I might try 4 and see what happens.

I’m also trying 0.001 as a step but that may be too granular so I think 0.01 is probably a good enough compromise.

If anyone else has any ranges they’ve seen or used that I could try out, please let me know.


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#4 2021-03-31 12:25:04

Bloke
Developer
From: Leeds, UK
Registered: 2006-01-29
Posts: 10,262
Website GitHub

Re: Range for gamma correction

Okay, just tried it with min => 0.25, max => 4, step => 0.01 and it works nicely. Anything above about 5 is silly. So I might stick with those values, or maybe stretch it to 5 just in case people want to get daft.


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