Photomerge>HDR create DNG with no preview so no thumbnail is shown in Windows Explorer

[turbodb]

Repro is simple (ish), at least for me:

Lightroom 13.0.2; Camera Raw 16.0; Camera: Canon R6

1. Use DNG converter to convert .CR3 files to DNG

2. Import DNGs into LR Classic 13.0.2

3. Select three (3) DNG files that are various exposures of the same image

4. Right click > Photomerge > HDR... (and just accept the defaults)

5. After the new DNG is created, look at it in Windows Explorer

Result:

The image has no thumbnail in Explorer.

Expect:

A thumbnail like all other DNGs. (including the ones that were used to create the HDR DNG file.

Note:

Attempting to open the HDR DNG in Windows Photos or Irfanview also gives a message about the DNG file possibly being corrupt. I suspect that this is just an issue with the Thumbnail, as LR 13.0.2 can still open/edit the file.

Note2:

When I try to attach an HDR file that I've created using the process above, which demonstrates the issue, I get the following error:

[moved from bugs to discussions according to the community rules - Mod.]

[JohanElzenga · Accepted solution]

This is a known issue. Lightroom uses a new compression method for these DNG files. Third party apps such as Windows Explorer may need an update to understand this.

[turbodb]

Gotcha, thanks. Seems strange, given that even trying to upload a DNG here (to adobe) gives an error about the contents of the file.

Can you point me to the location where this was discussed/identified as a known issue? I searched for quite a while last night and couldn't find anything.

[JohanElzenga]

I remember having read about third party apps not being able to handle the new DNG and needing an update, but I don't have a link.

[turbodb]

So, several more questions related to this as I think about it a bit more...

1. So, still the open question of why adobe.com considers these files to be corrupt when one attempts to upload them.
2. Why is it only HDR (and I assume pano) merges that cause this? I've created super resolution and noise reductions that don't cause this behavior?
3. Why don't updated thumbnails (Right click > Develop Settings > Update DNG metadata and thumbnails) use this new compression and cause problems?

[turbodb]

Sorry, one more bit to add here. Attached is a DNG created using the repro steps above, in case anyone is interested (and since I can't upload it here, and keep referring to adobe.com detecting it as corrupt)

2023-12-15-084455 18 emht - segment 3 - granite mountains - budweiser canyon - cactus (hdr).dng

https://onedrive.live.com/?cid=592B05F76554281F&id=592B05F76554281F%211348694&parId=592B05F76554281F...

[GoldingD]

Not at all related to your issues in your initial post, probably just a workflow preference on your part, but I have to ask:

1. Use DNG converter to convert .CR3 files to DNG

Why?

[turbodb]

Back when I "got started" with raw images, I think I was having some issue with the CR2 files (maybe no thumbnails?) in Windows. Or maybe some other image app I was using at the time, didn't support the CR2 files. Also, I wanted to have all the metadata stored in the file (no sidecars), which (again, at the time), I think needed DNG files.

Anyway, I've just stuck with that workflow, since it's worked well for me. 🤷‍:male_sign:

[GoldingD]

1. So, still the open question of why adobe.com considers these files to be corrupt when one attempts to upload them.
2. Why is it only HDR (and I assume pano) merges that cause this? I've created super resolution and noise reductions that don't cause this behavior?
3. Why don't updated thumbnails (Right click > Develop Settings > Update DNG metadata and thumbnails) use this new compression and cause problems?

1. This community site, when displaying images, uses your Operating system, not Lightroom Classic, to display those images. If your Operating System cannot display those images, then no display in this site.

2. Adobe, changed the way it compresses the DNG file in Merge Photo (not changeable by user), This involves a new DNG standard that has not yet been taken up by Microsoft or Apple or various third parties at this time. eventually they will.

LIghtroom Classic 13 HDR merge generated DNG file doesn't work with 3rd party softwarw | Adobe commu...

Panorama merge - something has changed but i don't know what or why - please help! | Lightroom Queen

3. Do you mean applying that to the Photo Merge DNG result? That will not undo the compression, that will not revert the DNG to a previous standard.

[turbodb]

1. This community site, when displaying images, uses your Operating system, not Lightroom Classic, to display those images. If your Operating System cannot display those images, then no display in this site.

The issue is actually that, when trying to upload the file, validation of the file contents compared to the DNG extension fails on the adobe server. It's not about displaying it locally on my machine.

2. Adobe, changed the way it compresses the DNG file in Merge Photo (not changeable by user), This involves a new DNG standard that has not yet been taken up by Microsoft or Apple or various third parties at this time. eventually they will.

Thanks! I'll check out those links, thanks. Seems strange to me that Adobe would do this, since it seems like they'd really want thumbnails on major OSes (esp MacOS), but hopefully Microsoft and Apple add support soon. 

3. Do you mean applying that to the Photo Merge DNG result? That will not undo the compression, that will not revert the DNG to a previous standard.

Let's see... how to make this clearer. I would have expected that a new DNG format (which seems like it was done for more efficient compression/storage) would have been used for all DNG saving, including saving any edits to DNGs that were created in ways besides Photo Merges (HDR, Pano, etc.).

However, I only see this "problem" with Photo Merged DNGs, I don't see it with DNGs that are imported (and then edited by LRC) from DNG converter, or DNGs created via Enhance (NR, SR). That just seems strange to me.

It means that Adobe has multiple "DNG output formats" in LRC, rather than a single persistence path. I would expect that a single path would be used, b/c if there's a "better"/"more efficient" format for Photo Merges, wouldn't it also be "better"/"more efficient" in the other situations as well?

[Jao vdL]

1. So, still the open question of why adobe.com considers these files to be corrupt when one attempts to upload them.
2. Why is it only HDR (and I assume pano) merges that cause this? I've created super resolution and noise reductions that don't cause this behavior?
3. Why don't updated thumbnails (Right click > Develop Settings > Update DNG metadata and thumbnails) use this new compression and cause problems?

By @turbodb

1. This forum does not allow raw files to be uploaded at all, only normal graphics formats such as jpeg and png. If you want to provide dng files, put them on a sharing site such as creative cloud drive, OneDrive, iCloud, etc. and put a link here. 

2. The more efficient compression method was only introduced in the last Lightroom Classic version. Before that they used a far less efficient compression method. The new method (it's jpegXL if you want to know) is far more efficient and still gives higher image quality. So if you made the other files before the update to Classic, those files are still using the old compression technique. You can see that from their much bigger sizes. The change to the new compression method is really good as it gives much smaller file sizes for the same or higher quality. Microsoft and others will catch up at some point. In the mean time you just have to deal with a generic icon instead of a picture in your file browser. The price of progress.

3. @GoldingD already explained this. Updating the thumbnail just replaces the existing jpegXL thumbnail with another one. If your operating system does not support that, it won't display it no matter how many times you update the thumbnail.

[turbodb]

1. This forum does not allow raw files to be uploaded at all, only normal graphics formats such as jpeg and png. If you want to provide dng files, put them on a sharing site such as creative cloud drive, OneDrive, iCloud, etc. and put a link here. 

Thanks, I didn't realize DNG uploads were allowed. The error in my initial post seemed to imply that they were allowed. (It recognized it as a DNG, but the contents didn't match the extension.)

2. The more efficient compression method was only introduced in the last Lightroom Classic version. Before that they used a far less efficient compression method. The new method (it's jpegXL if you want to know) is far more efficient and still gives higher image quality. So if you made the other files before the update to Classic, those files are still using the old compression technique. You can see that from their much bigger sizes. The change to the new compression method is really good as it gives much smaller file sizes for the same or higher quality. Microsoft and others will catch up at some point. In the mean time you just have to deal with a generic icon instead of a picture in your file browser. The price of progress.

👍

3. @GoldingD already explained this. Updating the thumbnail just replaces the existing jpegXL thumbnail with another one. If your operating system does not support that, it won't display it no matter how many times you update the thumbnail.

I mentioned this above to @GoldingD as well, but it seems strange to me that the jpegXL thumbnails are only used for Photo Merges and not for *all* DNG thumbnail saves. That is, if (in the current LRC version - 13.0.2) I make edits to a DNG that did not originate as a Photo Merge, I can update the thumbnail (Metadata > Update DNG Preview & Metadata) and it works correctly in Windows thumbnails. So, it seems that non-jpegXL thumbnails are still used for all DNG files that were not born of a Photomerge.

Even DNGs that "start life" as an Enhance (Noise Reduction, Super Resolution), have thumbnails/previews that use the old format (apparently, b/c they work in Windows).

Thanks again for all the answers! Really do appreciate it!