Histogram clipping indicators do not match Photoshop's

Explorer ,
Apr 11, 2022 Apr 11, 2022

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Using Lightroom Classic 11.2 on MacOS Catalina 10.15.7. But this issue has occurred for several years and versions.

 

Sometimes when I am editing a TIFF file in Photoshop, I use a Levels adjustment layer (or command-L) to set the black and white clip points to just before the histogram indicates clipping. When I save the file and go back to Lightroom Classic, on some files Lightroom's histogram indicates clipping even though Photoshop's does not. This seems to happen on files that have just a few very dark or very light pixels, so the left and/or right side of the histogram, before the adjustments, looks like a horizontal line just above the X axis. On such files, I can drag the clip points in farther before clipping is indicated in Photoshop than in Lightroom.

 

It is confusing that two Adobe editing programs bundled together disagree about whether clipping has occurred or not. This has happened in over a dozen files over the years. Sometimes I have to go back and forth between the two programs, repeatedly backing off the levels (or curves) adjustments in Photoshop and saving the file again, and checking it in Lightroom, before I can be sure I didn't clip anything.

 

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Community Expert ,
Apr 11, 2022 Apr 11, 2022

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These warnings say you are close to clipping, not that you have reached that. And it is clipping of the capacity of different working contexts and colourspaces that is being warned of. The exact same thing could be said of ACR vs PS, but we are used to the notion that those two editing contexts have different practical purposes and usages. And that the practical meaning of clipping won't be expected identical across the two. When two people who both normally wear size ten shoes, both put on size nine shoes - these smaller shoes will likely pinch or rub those two people's feet in different places. Just the same applies, when considering LrC vs PS.

 

Second, "nipping the edge" of clipping should in my opinion not be considered a workflow panacea (universal formula) anyway. Not all images even mind a little clipping: sometimes the picture works (unexpectedly) better with that in. Contrariwise, not all images do need to span the full extent of the histogram. Depends on what is in the photo, and what is the chosen pictorial representation.

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Community Expert ,
Apr 11, 2022 Apr 11, 2022

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LRs Histogram outside of soft proofing is always using Melissa RGB.

In Photoshop, the Histogram is based upon the color space of the rendered document. So you should expect to see a difference.

This might help:

Everything you thought you wanted to know about Histograms
Another exhaustive 40-minute video examining:
What are histograms? In Photoshop, ACR, Lightroom.
Histograms: clipping color and tones, color spaces, and color gamut.
Histogram and Photoshop’s Level’s command.
Histograms don’t tell us our images are good (examples).
Misconceptions about histograms. How they lie.
Histograms and Expose To The Right (ETTR).
Are histograms useful and if so, how?

Low rez (YouTube): http://www.youtube.com/watch?v=EjPsP4HhHhE
High rez: http://digitaldog.net/files/Histogram_Video.mov

Author “Color Management for Photographers" & "Photoshop CC Color Management/pluralsight"

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Community Expert ,
Apr 12, 2022 Apr 12, 2022

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@thedigitaldog wrote:

LRs Histogram outside of soft proofing is always using Melissa RGB.

In Photoshop, the Histogram is based upon the color space of the rendered document. So you should expect to see a difference.


 

That’s the most important point to understand here. It may not be obvious, but the histogram and clipping are measured based on the color space of the document. The applications aren’t actually “disagreeing”; in fact they would agree more closely if set the same way.

 

The demo below helps to show this. Lightroom Classic and Photoshop histograms shift consistently to follow the color space being used for previewing the image. If you set them consistently, the clipping points should be in consistent positions. Although I didn’t show Adobe Camera Raw, the difference is very obvious there: As you change the Color Space in Workflow Options among smaller and larger color spaces, in the preview window the on-image preview of clipping points shows more or fewer tones clipping. Which is absolutely and technically correct, because in a larger color space, you have more room before tones clip.

 

Histogram-vs-color-space.gif

 

I’ll leave it to someone else to explain why the histograms don’t look exactly the same for the same preview color space. Like I’m not sure why the Photoshop histogram for the same image has that bump to the right in the red channel, that is missing in the Lightroom Classic image. For ProPhoto RGB that might be explained by the slightly different tone curve, but I would expect them to be more similar in Adobe RGB.

 

But that doesn’t change the main point: If you set the preview color space consistently in Lightroom Classic, Photoshop, and Camera Raw, the clipping points should be at about the same place in all three.

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Community Expert ,
Apr 13, 2022 Apr 13, 2022

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When I set up a soft proof for Adobe RGB (1998) with a rendered Adobe RGB (1998) document (to make Melissa RGB go away), and compare it with Photoshop, the two Histograms match pretty well except for the vertical drawing which is based upon the number of pixels being represented. I suspect (key word suspect, hate to assume and could be totally wrong here) that LR isn't building this Histogram based on the original pixel density of (in this case) a TIFF like Photoshop. It's building the Histogram based upon the preview converted from source to destination color space. But the bottom line is, close enough and the horizontal axis is that's key along with clipping:

LRvsPSHisto.jpg

Author “Color Management for Photographers" & "Photoshop CC Color Management/pluralsight"

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