Refresh DNG-Preview not working

[berliner_ffm]

Since the latest release of Lightroom (ACR as well) the Refresh DNG Preview function is not working anymore. It will only embed a very small preview in the "PreviewImage" tag, but no fullsize preview as requested. 

Example DNG can be found here: https://u.pcloud.link/publink/show?code=XZPVYrVZJggbvp2qJhFu4qphbiYJnYuJMrfX 

[GoldingD]

 the Refresh DNG Preview function

The What?

Please pots a screenshot

[berliner_ffm]

Here is the menu item. This should refresh the DNG preview. The size setting for the preview can be set to "Full Size" in the application settings. However since LR 13 this is not working anymore. It pretends to create a new preview, but none is written to the dng file.

[GoldingD]

Ok, I looked right past it. I have no clue.

[GoldingD]

Is your problem anything like the one in this posting?:

https://community.adobe.com/t5/lightroom-classic-discussions/exif-lost-when-copying-dng-to-remote-fo...

[GoldingD]

This might be completely wrong, but???

In preferences, what do you have in this area:

[berliner_ffm]

This setting is set to "Full size".  All other Exif data is still present so I assume the problem is different from the one mentioned above. It affects basically all HDR-/Panorama-DNGs stitched in Lightroom. The don't include a full size preview by default no matter what setting is used, so the advice I got here in from the LR officials was to use the functionality to update the preview in Lightroom or ACR, which worked fine until LR 13 came out.

[felipeboca]

Same problem here....

[felipeboca]

Same problem here, the DNG file previews are terrible. I usually view files in the Mac finder or in apps like Photo Mechanic, but it's really bad. As said above, updating the file view through LR is not working.

[berliner_ffm]

@Rikk Flohr: Photography : could you please move this to the problems subforum and have a look at it. It is really a problem for any program relying on embedded previews. Thank you!!

[Rikk Flohr: Photography]

Please note the compression format used in DNGs (Panos and HDRs) was updated recently. I wonder if the issue is that the non-Adobe apps you are using to inspect previews are not yet supporting the DNG 1.7 spec. This is the case for Mac Finder and Windows Explorer as well. 

[berliner_ffm]

Hallo @Rikk Flohr: Photography ,

thanks for the hint. My understanding was, that the DNG itself uses some different kind of compressing since version 1.7 

But I am talking about the JPG preview embedded into the DNG. I opted to create a full size embedded preview, but all I got was a file which is noch much larger than an icon. See the linked image in my original post. Also when using ExifTool, it shows, that only the PreviewImage-tag exists, which contains about 12kb of data for a 20MP file.

No other previewtags like "JpgFromRaw" exist in metadata.

So while I understand, that the raw viewing might be limited in some applications, it seems, that this is not related to my problem. I need the fullsize jpg embedded in the DNG like the function in Camera Raw suggests.

If I am wrong, please tell me in which exif-tag the new preview is stored, so that I can have a deeper look at it, but so far I could not find any other binary data in the image that could be a match.

Again I am not talking about decoding the DNG to create a preview. I am talking about the embedded preview generated in Lightroom via the option shown above or the equivalent in camera raw.

Thanks!

[Rikk Flohr: Photography]

One of our engineers suggests using Bridge to interrogate the post-update thumbnail to see if it truly updates. Have you done this? 

[berliner_ffm]

Hi @Rikk Flohr: Photography ,

thanks for the suggestion. I installed Bridge, but when I try to see the images in Bridge it refuses to use the embedded previews (even though I selected the corresponding option) and instead renders a preview from the dng itself. So the question remains, how can I get Lightroom or ACR to embed a full size preview into the dng like it was possible until the recent update of Lightroom/ACR?

Thanks!

[berliner_ffm]

Hi @Rikk Flohr: Photography ,

do you have any update on this. Up to now, all new generated DNGs by Lightroom (eg. Panoramas, HDRs) do not contain any reasonable sized jpg-previews anymore. Refreshing those previews in LR Classic or ACR does have no effect. 

Could you either confirm this as a bug or let me know which exiftag in the dng attached to my first post holds the fullsize jpg preview? 

These previews are used by many programms so since the last update these images show up in an unusable low resolution.

[Rikk Flohr: Photography]

The engineers have left the following comments regarding your questions: 

First, this does not appear to be a bug. 

The largest preview size currently used in the DNG is now a JXL format.  If your non-Adobe software does not support this format, then you will not be able to see/use that preview. 

If you need a DNG with updated previews and an older DNG version, as it appears,  you will need to export a new DNG file with the compatibility version set to an older version. Have you tried this?