Severe contrast enhancements: on 45% rule — and cats

Started Jun 28, 2013 | Discussions thread
knickerhawk
Veteran MemberPosts: 3,297
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Re: Changing contrast without distorting colors: 45% rule and another cat
In reply to ilza, Jul 11, 2013

ilza wrote:

knickerhawk wrote:

I'm pretty slow at this stuff too. To make things worse Ilza has marked me as a humanities major

Come on, all I said was that you behavedlike one. My apologies if you really took this simile too seriously!

presumably incapable of understanding the difficulties involved. However, I'll muddle on as best I can...

“Capability to understand” is a two way street. You not understanding me may be interpreted as your stupidity, or my ineptness, or just an impedance mismatch.

And I would say that for a humanities major, you muddle wonderfully!

On crappiness: IMO 45% is always better than 0% and 100%; but to find the best percentage more precisely, one needs either to consider a very large pool of images, or some extreme case, where the differences between 40%, 45%, 50% are more pronounced. I thought that γ=5 would provide a good example of such an extreme case; and to have something visible after γ=5, one must start with something sub-optimal.

Well, this was my logic in choosing this image as an example. In hindsight, it has obviously failed. Do you have better ideas for examples?

I don't have Gimp installed and haven't used it, so I'm not sure what y=5 corresponds to in any scaling available in Photoshop. I'm also having difficulty understanding the problem you have with a straightforward curve adjustment set to blend in luminosity mode or a curve adjustment to the L channel in LAB. Depending on the contrast already present in the image, both work well without f'ing up color. Here's a quick and dirty luminosity blend of your image. Hue hasn't been changed by it. (The cat is sitting at the bottom of the rock pile a little more than a quarter of the way in from the right.)

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