Lightroom/Camera Raw: Converting raw files to lossy DNG sometimes results in purple-cast previews in the Library module

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  • Updated 5 days ago
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  • (Edited)
I convert whole folders of raw files to lossy DNG on a regular basis, and since earlier this year (at least), I've noticed a problem that affects a very small percentage of the files (sometimes it doesn't happen at all), but it's starting to become a little annoying.

The problem (when it happens) is that some of the resulting lossy DNG files look good in the Develop mode of LR Classic and in Camera Raw. Even the preview from Windows file explorer (and when using image viewers that display the embedded jpg preview) looks ok. But when displaying these problematic files from the Library module in Lightroom Classic, they show a strong purple cast. So, I think there is some problem with the preview generated by LR.

Like I said, this problem happens very rarely, but it keeps happening every now and then. Most of the times I am able to fix the "pink preview" by re-building 1:1 previews, or just removing and reimporting the file. But there must be something going on with the preview generation for lossy DNG files since I also read about it (or a very similar problem) in this thread: https://forums.adobe.com/message/10758722

I am using Windows 10 and the latest versions of Lightroom Classic CC (8.0) and Camera Raw 11.0, but this was happening already with some LR CC 7.x versions. Thanks.
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Carlos Oliveras

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  • purple-ish

Posted 4 weeks ago

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Christian Fürst

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sounds odd....
2) I was of the opinion that DNG is "lossless" ???????


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Carlos Oliveras

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There are both flavors, lossy and lossless DNG. Unfortunately, they both share the same .dng extension, which (in my opinion) is a little confusing. But that's a different story unrelated to this problem, of course.
Maybe this issue happens too with the lossless version of it, but so far I've only experienced it when converting to lossy (which is what I use most of the time).
(Edited)
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Chris Castleberry, Camera Raw Engineer

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Hello Carlos,

If possible, will you please post a download link to some examples of source raw+lossy DNG pairs where this is occurring for you?

And please note the exact DNG conversion settings as well.

Thank you!

Regards,

- Chris
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Carlos Oliveras

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Hey Chris, thanks a lot for your interest. It's a little hard for me to find examples (because when it happens, I usually rebuild previews until the problem is gone, and also, when I convert, I delete the original raw files at the same time). But thanks to some backup copies, I've been able to locate a couple of raws where this happened later on when I converted them to DNG. 

I don't know if it's relevant, but they were shot in raw+jpeg mode, so I'll include the jpeg just in case. Also, while I only find this issue every now and then, in this case it affected 2 files in a row, and I've found another case where also 2 files in a row were affected. It doesn't seem like a coincidence...

Anyway, you can download the files here (I've included a screenshot of how they look in my LR library):

http://photoshopeando.com/descargas/otros/purple_cast.rar (78 MB)

I will include an image with the settings I use every time I convert a folder of raw files to lossy dng.

Anyway, I am not sure you will be able to replicate the problem with these files because normally, if I remove and reimport the "pinkish" dng file (from LR Classic CC), the issue is gone. In fact, I've tried to re-convert these raw files to dng with a new catalog, and the issue didn't happen. So, maybe there's nothing special about the files themselves... maybe there's something else, but I can't see the trigger or pattern.

Please let me know when you've downloaded the .rar file so that I can delete it from my server (but there's no hurry). Again, thanks a lot for your interest in looking into this.


(Edited)
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Chris Castleberry, Camera Raw Engineer

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Thanks, Carlos. 

I am unable to reproduce this so far, but as you mentioned the behavior seems intermittent. After checking our internal bug database, there was a similar issue fixed for the last public release of Lightroom Classic CC version 8.0. However, there is still the possibility of the bug occurring under certain conditions such as a threading race condition, which might explain the intermittent reproducibility you have been experiencing. If you have updated to Lr Classic CC 8.0 and still see this happening occasionally, please let me know.

Regards,

- Chris
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Carlos Oliveras

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Thanks for having a look at this and trying to reproduce the problem, Chris. Yes, I am using LR Classic CC 8.0 (build 1193777).

Like you say, it seems like something intermittent. So far it hasn't been a huge problem (in fact, it happens very rarely, and while it's annoying, it's also easy to fix), but from now on, I'll try to pay more attention when converting files, just in case I notice any pattern or possible trigger. If so, I would post any finding in this thread, in the hopes that it can provide some clue. Or maybe it won't happen again! (I'll keep my fingers crossed).

Kind regards,

Carlos
(Edited)
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Kent Hinson

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Hello. I am also having this issue. Using Adobe DNG converter 11.1.0.112. on Mac OS 10.14. Some images the color is correct but some come out red or pink. This only happens when using compression. If I do a non compressed convert then no color problems occur. 

The strange thing is it's not all of the files only some from my camera turn pink. however when it does happen it's 100% repeatable. I can't ever compress that file without it turning pink or red. 



I'm assuming that Photoshop and DNG converter share a code base and therefore are sharing this bug? Also it seems to be platform agnostic as I'm on OSX and the OP is on windows.

Here are some example files, original, converted uncompressed, and converted compressed.
https://drive.google.com/file/d/1onG6M0QAlypEAQ7X5xC4iaIsOnMN9rhq/view?usp=sharing



UPDATE:
I tried this now.
Convert Cr3 to DNG(uncompressed) with DNG converter 11

Then I used DNG converter 7.2 to convert that DNG(uncompressed ) to DNG(Compressed)

That worked! No color issues. So it seems that the newer DNG converter has a bug that is not in the older software. 






Chris Castleberry can you comment on this? Is this the right place to report this issue or should it be forwarded to somewhere else?


(Edited)
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Michelle Qi, Employee

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Hi Kent, we are having trouble reproducing this issue in house on Mac OS 10.14 (and 10.13) using DNG Converter 11.1. We also tried with your .cr3 image - still can't repro. Two questions:1. Are you positive you are using DNG Conveter 11.1.0.112? you can find this info by clicking on "About DNG Conveter"
2. Can you always see this issue with just converting this .cr3 file by itself or with a bunch of other files?
3. Could you provide more details on the exact step you did with "This only happens when using compression"? Perhaps a screenshot?


Thank you.
Michelle Qi
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Kent Hinson

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Hi Michelle!

Yes I am sure.


2. Yes every time I convert this cr3 file it is pink when using (v11) with compression on. By this I mean Change Preferences -> Check Use Lossy Compression.

3. If I convert the cr3 file to dng with no compression I dont see pink. (v11). By this I mean Change Preferences -> Uncheck Use Lossy Compression.


4. If I take the dng file from step 3 without pink and run it though v11 again this time with lossy compression on it will also be pink.

5. If I take the dng file from step 3 without pink and run it though v7.2 this time with lossy compression on it will not be pink and it will be compressed.


Basically right now I have to run the file through two different versions of DNG converter first to go from cr3 to dng(uncompressed) then the second to go from DNG to DNG(compressed)


Also to clarify. Some photos turn out pink when being converted and some don't. But they are consistent. The ones that will turn pink always will turn pink no matter how many times I run the software on the cr3 file.

Additional information. They dont all turn pink. Some turn red. Some turn a copper color like a old sepia photo. but whatever color they turn is consistent every time they are converted.
(Edited)
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Michelle Qi, Employee

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Thank you Kent for your responses and detailed info! We can reproduce what you're seeing in the Finder/Preview. This appears to be an issue with Apple’s preview software. We’ve logged the issue with Apple. Hopefully they will fix it in an upcoming OS release.

Thanks again.
Michelle
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Kent Hinson

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Michelle please let me know if you need more information or some kind of log file. I'm happy to help get it fixed.
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Kent Hinson

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Hi Michelle. Thanks for the info. I'm curious why is 7.2 ok but not v11? Am I loosing some image data using 7.2 to compress verses using v11?