Image tone changes from Lightroom to Photoshop

[Jamie Farquharson]

Hi there, this is quite an embarassing problem, and I cannot find the solution.

If I process an image in Lightroom Classic, and edit it in Photoshop, the copy that has opened in Photoshop has different tones. 

I am using the Adobe RGB colour space in Photoshop, and Lightroom's External Editing colour space preference is set to Adobe RGB, and Bit Depth is at 16bit. 

I am using Photoshop 26.6, Lightroom Classic 14.3, and Camera Raw 17.3. The computer is a Mac Studio M2 Pro, Sonoma 14.4.1.

Attached are files showing the difference between the LR and PS images, plus the relevant LR and PS settings.

Please help! I have alway been winging it with colour space and profiles, but this one has me beat. 

Thanks, Jamie

[LAMY2017]

These problems always take more time and intelligence than I have, Jamie.

What does Ps say for your color profile?

I wouldn't typify your issue as "tone," but levels/brightness.

[Jamie Farquharson]

Hi Larry, the PS image is using the AdobeRGB profile

[LAMY2017]

I compared Levels of Lr vs Ps; I see that the Lr image's background looks lighter than the Ps image.

The histograms as seen in Photoshop Levels between 0 and 2.8 look "holier" for the Lr image than the Ps image.

The Lr image's Hue looks a little bluer than the Ps image's hue.

[Jamie Farquharson]

Thanks Larry. Those example images I sent aren't great, it's not so easy to see what the problem is. I want a dark image, but they aren't so dark in PS or LR, and easier to see the issue.

I have been combing the forums, and it looks as though this is a problem with the M2 chip, GPUs and Adobe. Switching off GPUs in LR and PS has "fixed" the problem, if I take an image from LR into PS there is no tonal difference anymore. But I'm not sure how happy I am with this solution. Going to read some more...

[D Fosse]

This is an issue that has been reported from several Mac users lately. The symptom seems to be the same: excessive black clipping in Lightroom compared to Photoshop.

I would start by determining which of these two is the correct representation. That's pretty easy to determine. Take screenshots of both, assign your monitor profile, and convert back to Adobe RGB. All the 3 histograms - original Adobe RGB file and the two screenshots - should now be a perfect match. If they're not, the odd one out doesn't display the file correctly.

So far, all the signs point to a bug in MacOS - specifically, the GPU driver component in MacOS. It could be an Adobe bug, but if so, it's specific to the Mac Photoshop version. This has never been reported from Windows, and cannot be reproduced by Windows users who have tried (including myself).

And if, as you say, disabling the GPU clears it, that's further confirmation.

[Jamie Farquharson]

Hi D,

Thanks for your reply, I have been reading your posts about this issue, your diagnosis of the problem is amazing!

I will be following your instructions as to whether PS or LR is the source of the problem tomorrow. This is well out of my comfort zone, and a day spent searching for answers for this has finished me. 

One other useful piece of information I found was from user rvdknl in the Apple forums. He says in the post "Lifted and desatured blacks in Photoshop" that switching from Adobe ACE to Apple CMM in PS's colour settings virtually fixes the issue. Colours and tones match between LR and PS, with very minor diffrences in deep blacks. I have tried this and I can confirm.

Again, thanks for your reply, it came at just the right time,

Jamie

[D Fosse]

One other useful piece of information I found was from user rvdknl in the Apple forums. He says in the post "Lifted and desatured blacks in Photoshop" that switching from Adobe ACE to Apple CMM in PS's colour settings virtually fixes the issue.

By @Jamie Farquharson

Yes, that has also been reported here. For some it corrects it completely, for others some of the way. Of course, both color management engines should produce the correct result. This isn't open to interpretation.

Figuring out which version you can trust should at least give you some firm ground.

[Jamie Farquharson]

Good Morning D,

I have started the diagnosis process as you detailed above, but have to confess, I have got a bit lost. Here is where I am:

Take screenshots of both,

Screenshot taken from LR, with GPU on. 

Screenshot of same image, taken from PS. Conversion Engine is Adobe ACE in colour settings.

Are these screenshots taken under the right conditions for this test?

assign your monitor profile,

Problem here- Both screenshots are using the monitor profile by default so I cannot re-assign the monitor profile. Where have I gone wrong?

and convert back to Adobe RGB. All the 3 histograms - original Adobe RGB file and the two screenshots - should now be a perfect match. If they're not, the odd one out doesn't display the file correctly.

I have trouble working out where I get the original RGB file from. Is it simply the same image used for the screenshots opened from LR into PS, or am I hopelesly off base?

Sorry for asking for clarification, in my opinion you have already gone above and beyond with this. I feel like I'm really close to grasping it, and I just need a couple of pointers to complete the process. I'm really looking forward to getting to the bottom of it, and hilst it's nicer to have closer matching images now, as you said in your reply last night, both colour management engines should be producing the identical result, and we want to know why they aren't.

Best regards,

Jamie

[D Fosse]

First open the file from Lightroom into Photoshop, in Adobe RGB. This is your original RGB file. The assumption here is that the raw file is correctly processed and encoded into Adobe RGB (there has never been any reason to doubt that).

The histogram for this Adobe RGB file is the reference. Make a screenshot of that histogram and keep it.

Next, take two screenshots of the image itself, one from Lightroom Develop and the other from Photoshop. If the monitor profile is already embedded here, you don't do anything, that's fine (on Windows a screenshot is untagged and you need to assign the profile).

Open both image screenshots in Photoshop, with the monitor profile embedded. Convert both from the monitor profile to Adobe RGB. So now you have two Adobe RGB files that started out as screenshots. The interesting part here is the histogram, so again screenshot those and keep them.

What you have now is three histograms. Since they now all refer to the same color space, Adobe RGB, they are directly comparable and if the images they come from are identical, the histograms will also be identical.

Here's the background for the procedure:

The numbers sent to screen are no longer in the original color space, they have already been converted into monitor color space. So that's the correct profile here. However, numbers are color space specific, so to be able to compare these, they need to all be brought into the same color space.

EDIT addition: there is one factor that can introduce small differences, and that is noise. If the on-screen image is zoomed out/scaled down, different screen resampling algorithms can produce slightly different results. For this reason, either use a low-ISO image with very little noise (Denoise is an option here) - or use an image that is small enough to fit on screen at 100%. This isn't the reason for what you're seeing, but just to remove complicating factors from the equation.

[Jamie Farquharson]

That's great, thankyou! I first saw your message as an email, and carried out your instructions from that. I missed your edit about using a low ISO image. My test image has an ISO 0f 1000, but I think the principle still stands.

Having been through the process, it's the LR histogram that is the odd one out. Attached are the images with the histogram. I'm not sure if it will be possible to see the difference in this forums viewer, it's very indistinct in my original post, but the histograms make it clear.

Also, the attached file "LrScreenshot-NoGPU" is a screenshot of LR with GPU switched off and then put through your process. It's closer to PsScreenshot and _DSC3458-P than LrScreenshot, but still not precisely the same. As a temporary work around it will do, but what would you suggest the next step is?

Thanks again for your time,

Jamie

[D Fosse]

OK. Yeah, I just repeated the exercise myself, and I discovered that noise needs to be eliminated unless you have a small file that can be displayed in full at 100%. Excessive noise adds a lot of dark values that disappear when downsampled. The noise influences the "original" histogram, but not the two "screen" histograms because they are already downsampled, killing the noise.

One way to get around this is to downsample the original RGB file before screenshotting the histogram, so that it fits the screen at 100%. That gets rid of the noise, the same way as for the other two image screenshots. In other words, this levels out the playing field.

Here's what I got (see the file names):

As you can see, Photoshop is pretty dead accurate. Lightroom (displaying the raw file) is ever so slightly off in the far darkest values, but there's no way I'm able to see that difference using Eizo coloredge monitors. For all practical purposes, these are identical.

Note that this measures the accuracy of the GPU/color management and your monitor profile combined. I don't know of any way to separate these two components. So if you don't get a match, rerun your monitor profiling first.

[Jamie Farquharson]

Hi again D,

Thanks again for all your help. I'd like to approach Apple and Adobe about this, and specifically use your historam diagnosis method to show them where the problem lies. I it OK if I mention you and your (incredible) contribution?

[D Fosse]

No problem. Good luck 🙂

[NB, colourmanagement]

@Jamie Farquharson "Switching off GPUs in LR and PS has "fixed" the problem" 

yes, sadly you might be stuck with that for now 

I hope this helps

neil barstow colourmanagement - adobe forum volunteer,

colourmanagement consultant & co-author of 'getting colour right'

See my free articles on colourmanagement online

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