Severe contrast enhancements: on 45% rule — and cats

Started Jun 28, 2013 | Discussions thread
ilza
Forum MemberPosts: 74
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Re: Changing contrast without distorting colors: 45% rule and another cat
In reply to ilza, Jul 10, 2013

I wrote:

What you describe in this reference is, essentially, “the 100% rule”: you keep the saturation of the initial image intact. This is the “variant 2” of my post (with the variant 3 being the “the 0% rule”).

The whole topic of my post was that your method gives unnatural colors; hence “the 45% rule”. For my eyes, 45 gives visually better results than “the 40% rule” or “the 50% rule” — which are both significantly better than “the 100% rule” or “the 0% rule”.

To be more convincing, try “10 pictures are better than 20 words” approach.

  • Start with another popular “Find a cat” image (“Camouflage cat”; again, I could not find proper attribution);
  • Increase contrast ×5 (in GIMP, it is called γ=0.2: go to Colors/Levels, change the middle number);
  • Keep the original’s hue;
  • Keep a N% of the original’s saturation (N% rule; HOWTO-in-GIMP in the OP; changing is just moving one slider).
  • Compare the results for various values of N (below, 0, 40, 45, 50, 100).

The original (Camouflage cat)

γ=5, 0% rule (the variant 3 of the OP: apply curve to RGB, keep original’s hue)

γ=5, 40% rule

γ=5, 45% rule (for my eyes, the best match for the original’s colors)

γ=5, 50% rule

γ=5, 100% rule (variant 2 of the OP: keep hue and saturation of the original; this is what everybody else in this discussion thinks/thought is the best way to do it).

Judge for yourself… (BTW, I do not think that the contrast enhancement here helps with identifying a cat in any way. Did it help you?)

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