Lightroom Highlights and Shadows Artifact

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I am experiencing what I find to be a rather serious "double-edge" artifact that I have isolated to Lightroom's (and Adobe Camera Raw's) Highlights and Shadows sliders.

I first reported and documented the problem here: https://forums.adobe.com/message/8833203#8833203

where it was suggested that I also report it on this forum.

Do I need to recreate my posts here, or is providing the link to the thread on the other Adobe forum sufficient?

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Keith
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Keith Diefendorff

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Posted 2 years ago

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Todd Shaner, Champion

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The LR Forum link is fine and I have added the link to this report at your original post in the LR forum.
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Todd Shaner, Champion

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There is another report with the same issue, which was originally thought to be caused by excessive Clarity setting. It clearly shows the same Highlights and Shadows edge artifacts. https://feedback.photoshop.com/photoshop_family/topics/artifacts-on-edges-caused-by-clarity
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Simon Chen, Principal Computer Scientist

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Hi Todd, 

It would be nice if you could share a raw file with settings that exhibits this issue so that the team can investigate.

Thanks,
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Todd Shaner, Champion

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Simon, a similar issue is reported as 'In Progress' at the link I provided: https://feedback.photoshop.com/photoshop_family/topics/artifacts-on-edges-caused-by-clarity

It was originally thought this issue was being caused by the Clarity control, but later identified as due to the Shadows and Highlights controls. An ARW raw file share link is in the above post.

At the link provide by Keith Diefendorff in this problem report the issue can be clearly seen using a PS document with a black rectangle on a white background.

Please let me know if I can be of further assistance.
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Steve Sprengel, Champion

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In my opinion the issue in this thread is about a reverse-gradient halo along the entire edge, but the issue in the other thread you link to, is something else:  the alternating light and dark "spikes" one pixel wide along a diagonal edge that has Clarity applied, like a demosaicing error has been accentuated. 
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Todd Shaner, Champion

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Steve, I think it's the same issue. I created a 1000x1000 pixel white rectangle in PS and then placed a black rectangle on one file and a black circle on another file. I applied a 2.0 pixel Gaussian Blur to both files. Inside LR I applied -100 Highlights and +100 Shadows and Sharpening 25, 1.0, 25, 0. Here's the results:
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Simon Chen, Principal Computer Scientist

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I could reproduce the issue. I've talk to others on the team and can confirm that this is a known limitation of the current technology, especially on high contrast transition edges like this. One workaround is to apply the +clarity on the select area of the photo. For example, you could use the local brush to paint back and reduce the clarity along the edge. I can get reasonably good result by brushing -100 clarity with a large radius and feather. Or you can paint +clarity only in areas that are required, well away from the edge.
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Keith Diefendorff

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I just tried painting a +100 Clarity bush stroke across the edges of the black-on-white test-square image that I first posted. The Clarity strokes had almost no effect on the vertical edge of the square. It did have an effect on the horizontal edge, but it wasn't much of an improvement. It erased some of white band but moved the dark band outward, which is in some ways worse. Even if it did work, it doesn't seem like a very practical workaround anyway.

I'm not sure what you mean by "limitation of the current technology."  The Photoshop CC Shadows/Highlights adjustment does not produce this artifact. It is only ACR (and LR).

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Keith
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Simon Chen, Principal Computer Scientist

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Photoshop CC Shadows/Highlights implementation is different from that of Lr/ACR (PV 2012) and has its own limitations.
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Todd Shaner, Champion

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Simon, the same artifacts are also created with -Highlights and/or +Shadows with no Clarity adjustment applied. When using PS's Shadows/Highlights adjustment panel with similar settings these artifacts do not occur. One of the possible solutions I suggested to Eric Chan was to use different processing for Export, Edit in PS, and perhaps even Library preview building that doesn't produce the artifacts. This maintains real-time performance in the LR Develop module, but provides better rendering for tasks that can be performed in the background. Just a suggestion.
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Giuseppe Covino

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I have the same problem setting hightlight recovery to -50 or less (for example to recover a white sky), an ugly double border is created by Lightroom in edges, see below on the left image

The lens "remove chromatic aberration" is not the cause, infact the right image is with CA removal off and the bad effect is still there.
This is something I had not seen in the past (like a couple of years ago and before) so I think it has been introduced later.
Sorry but it think it must be fixed, it is not possible to brush paint all the edges to try to eliminate those artifacts.
Thanks

Giuse