Lightroom/Camera Raw: Local contrast adjustments that are actually localized

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  • Updated 7 years ago
Currently, the contrast slider in Adjustment Brush tool is a modifier on the global contrast. If your adjustment brush mask covers only highlights (e.g. an overexposed sky), then contrast ends up working backwards -- increasing the local contrast will compress the adjustment area, while decreasing local contrast will increase the visible detail in the clouds.

I wish for a contrast slider that would operate only on the area covered by the brush. Increasing local contrast would visibly increase contrast in the masked area, and vice-versa. It would locate the darkest and lightest areas in the masked area, and adjust the curvature of the S-curve between those dark and light points.
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Mark Sirota

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Posted 7 years ago

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Lee Jay

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I can imagine some problems with this approach, but not many solutions.

What if you're adjusting a dark area, and things are going just fine, when suddenly you slide over a single all-white pixel (like, for example, a tiny specular highlight on a ring or something)? Would the entire adjustment you've just been making suddenly revert to what we have now because that pixel so severely altered the entire range in the selection?

What about feathering? Should any pixel under even the weakest part of the brush's feather affect the total range used in the same way, or should there be some sort of weighting factor for that?
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Mark Sirota

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For the first, I think a 95/5 calculation for the endpoints would work. In other words, toss out the darkest 5% and the lightest 5% when determining the range.

On the second, I'd think weighting the importance according to the feather makes sense, though it's probably computationally expensive. Experimentation during the R&D process would probably reveal the proper strategy.
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Rob Cole

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Mark, the only thing I don't like about this idea is that *I* didn't think of it ;-}. Anyway, I wouldn't know the best way to resolve the various issues that might come up during implementation, but Nik has a similar tool:

Consider Nik Software's 'Tonal Contrast' tool in their ColorEfexPro plugin (NX2 & Photoshop). - it has sliders for weighting local contrast adjustment in the highlights, midtones, and shadow regions. Lightroom's Clarity is very much like the midtones subset, only Lightroom's implementation is better, IMO.

Fill-light goes a long way in providing tonal separation in the shadows, but can't be applied locally. And, the only way to get good highlight separation without compressing midtones is to reduce contrast locally - recovery doesn't cut it very well.

Summary:
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Intelligent (adaptive) algorithm for local tone separation would be awesome! - and I clicked the '+1' button to show my support.

See related thread: Highlight *Detail* Recovery.
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TK

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What about being able to set a "working point" for contrast manually?
I almost never use the global contrast slider because I cannot control the gray value it uses to separate the extreme values from.

If we could control around which value other values become "stretched" it would increase the utility of the contrast slider and provide a (manual) solution for your problem as well.

Ideally one could control the lower and upper values that are affected by a contrast adjustment as well. Otherwise, in the scenarios you mention, the adjustment will be asymmetric.
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Rob Cole

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TK - although I like your idea, the Lr tone curve already covers the global case of this (granted requires more fiddling), right?. And localized application of tone curve is an idea HEART-BREAKINGLY under-appreciated in the photography community (which would cover the local case...).
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TK

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Yes, it should be possible to freely apply tonal changes locally. However, many times full tone curve control is not needed.

And yes, I can achieve my custom contrast using the tone curve but it requires moving quite a number of sliders and/or setting of points.

Why not put the contrast slider to actual use by making it more flexible? I reckon many people use it despite it almost never getting the "working point" right (because the latter depends on the image), but this results in suboptimal adjustments which are undesirable.
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Rob Cole

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I see your point TK. tone curve is overkill when all you want is a smooth 'S' with a different mid, left, and/or right points.