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Lightroom: Different histograms for identical copies of a raw file
Develop displays histograms for identical images with small but noticeable differences, and these differences depend on the order in which you edit the files. By itself, this probably doesn't have any impact on users, but it may indicate a worrisome underlying bug in how Develop caches computations.
See this screen recording, and follow these steps precisely:
1. Download this sample raw into a folder and make a copy of the raw in the same folder. Rename the two raws A and B.
2. In LR, do Preferences > Performance > Camera Raw Cache Settings > Purge Cache.
3. Restart LR.
4. Import A and B.
5. In Library, select A and make a virtual copy.
6. In Library, select A and Cmd-click B (order is important).
7. Go to Develop, and use the cursor keys to switch between A and B. The histograms appear identical.
8. Go to Library.
9. Without changing the selection, go to Develop, and use the cursor keys to switch between A and B. The histograms now have small but noticeable differences.
10. In Library, select A and Cmd-click the virtual copy (order is important).
11. Go to Develop, and use the cursor keys to switch between A and the virtual copy. The histograms have small but noticeable differences.
Tested on LR 8.3.1 / Mac OS 10.14.5.
See this screen recording, and follow these steps precisely:
1. Download this sample raw into a folder and make a copy of the raw in the same folder. Rename the two raws A and B.
2. In LR, do Preferences > Performance > Camera Raw Cache Settings > Purge Cache.
3. Restart LR.
4. Import A and B.
5. In Library, select A and make a virtual copy.
6. In Library, select A and Cmd-click B (order is important).
7. Go to Develop, and use the cursor keys to switch between A and B. The histograms appear identical.
8. Go to Library.
9. Without changing the selection, go to Develop, and use the cursor keys to switch between A and B. The histograms now have small but noticeable differences.
10. In Library, select A and Cmd-click the virtual copy (order is important).
11. Go to Develop, and use the cursor keys to switch between A and the virtual copy. The histograms have small but noticeable differences.
Tested on LR 8.3.1 / Mac OS 10.14.5.
Responses
kelly_castro
87 Messages
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2.1K Points
2 years ago
It looks like the download link to your sample bug file has expired. Can you please repost it? I have yet to be able to reproduce the issue using various RAFs.
Thanks,
Kelly
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kelly_castro
87 Messages
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2.1K Points
2 years ago
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kelly_castro
87 Messages
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2.1K Points
2 years ago
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todd_shaner_6660895
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38K Points
2 years ago
1. If you apply any Develop setting to the DNG file and then set it back to 0 the histograms match.
2. They will also match if you simply click on the reset button with the DNG file selected.
3. Zooming to 1:1 view in the Develop module the histograms remain different.
4. Zooming to 1:1 view in the Library module and back the histograms then match at all Zoom views.
I tested LR 8.2 with the Export module set to Compatibility Camera Raw 11.2 and later (i.e. matching versions) and it exhibits the same issue. I also tested LR 5.7.1 and it does NOT exhibit this issue.
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Rikk
Adobe Administrator
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7 months ago
Quality Engineering - Customer Advocacy
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John_R_Ellis
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7 months ago
Here's a Photoshop difference of screenshots of the two histograms (click to see it larger):
I don't think this has any practical impact on users -- as a developer, I'd just worry that this is symptomatic of a more serious bug in how Develop or ACR caches computations.
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todd_shaner_6660895
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7 months ago
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