LIGHTROOM - CLAHE / local contrast enhancement

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A long, long time ago (1985) I invented the CLAHE (Contrast Limited Adaptive Histogram Equalization) which is a pretty good way to enhance local contrast in images. I published source code of this method in 1994 - and to my surprise, that article is frequently cited in new work that uses CLAHE in application areas like underwater photography, traffic control, astronomy, and medical imaging.

While folks created CLAHE plugins for a variety of applications (darkroom, MATLAB, imageJ - this plugins usually use my original implementation as a starting point), I have yet to see an implementation in an Adobe product. I'd love to be able to apply CLAHE on my own pictures in Lightroom.

Any plans for CLAHE in lightroom? Anything I can do to make that happen?

Cheers, Karel
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Karel Zuiderveld

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Posted 4 years ago

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John R. Ellis, Champion

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How does CLAHE compare in capability and image quality with one of the core algorithms used by LR, Local Laplacian Filters? See http://blogs.adobe.com/lightroomjourn...
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Karel Zuiderveld

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I'd have to review the LR article, but on first glance local Laplacian filters provide edge sharpening - no edges, no effect. Dark homogeneous areas will stay dark, which is definitely not the case with CLAHE.

I suspect that a hybrid of the two methods will be even better (CLAHE sometimes has issues around edges (halo effect) which could conceivably be fixed by some form of edge processing).

You probably can make your own assessment wrt CLAHE capability and image quality by Googling on "clahe color images".
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John R. Ellis, Champion

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LR 5's Clarity adjustment demonstrates one of the applications of the algorithm.
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Karel Zuiderveld

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Ah, OK. I usually add Clarity to my images to enhance the edges (I thought that Clarity was a simple unsharp mask, but I guess more is going on there), but it certainly does not enhance local contrast the way CLAHE would do on those images (as in: I think CLAHE would work better on some images I try to process).
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John R. Ellis, Champion

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I'm at the edge of my knowledge about LR's image algorithms. But if you want to catch Adobe's attention, you might include some comparison photos here. Adobe does read this forum (and infrequently responds).
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Karel Zuiderveld

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Yeah, and that's the chicken and egg problem. The whole reason for this request is that I do not have a convenient way to calculate CLAHE; I just noticed that many other folks are publishing work using the method, so it's working well for them.

Oh well, it's up to Adobe to follow up with me - I published C++ source code for CLAHE, they should be able to get the algorithm in no time and do some A/B comparisons themselves to judge whether it is worth further consideration.