DNG files not displaying thumbnail

FWIW I just downloaded one as a trial- and a thumbnail is displayed.

I picked the last one...
LEICA M9 Sample Images and DNG files

Feel free to provide a link to one for which you don't see a thumbnail.

That sample file on the linked site works fine in my Win11 and Photos and Windows Photo Viewer, shows thumbnail in Medium icons, Large icons and Extra Large icons view but not in Small.

As folders may have hundreds of files

This may be an issue with quantity rather than the file type.

Consider
Change Icon Cache Size in Windows
and
Clear and Reset Thumbnail Cache in Windows 10 | Tutorials

The second might be what you've already done.

(The searchable Tutorials section is invaluable).

And thank you for your reply. Good luck.

dalchina said:

And thank you for your reply. Good luck.

I have just used the Reg file to increase thumbnail cache - didn't know that was an option - thnx

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Daymin said:

Oldnewexplorer might help with that.

.DNG ( Digital Negative ) is literally an international raw file type to be used cross platforms without any discrimination. It's main goal is to counter Cannon RAW, CRAW2, and any other file time to prevent marketing of the RAW file only for Canon. SONY for instance uses the RAW format which in a nutshell is better.

When you shoot you shoot in RAW no matter the format. Always RAW because JPEGS are pugly garbage. Pop into Camera Raw via photoshop as a group/folder and edit/update etc. Same with Light Room

A good chance you just should use the JPG as the reference, via the date number, and separate them into another folder.
I use "Irfanview" to organize my images, as it will open the RAW file as best it is able to and display the JPG thumb ( if one is present ) in the RAW file.

My workflow (at the moment) is to copy RAW + Jpeg to a sub folder in My_Pictures.
Then import into Light Room. I don't separate out, I'll give that some thought.

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After Cache clear and size increase as per post #4.
This pic gives a good 'view' of the issue.
JPEG have thumbnails.... DNG don't but with enough time the DNG turns first to a block of colour as can be seen by 2 of the files ..... eventually (Hr+) they will turn into thumbnails ...... but still leave some DNG files as no thumbnail.

No need to over think this. Windows will display a thumbnail preview(image) on any file provided you have the proper app\program installed. all you need in your case is raw image viewer. You can usually get one at your camera makers website or you can use a generic freebie like the one below (dng viewer). It's small (2.36mb installed) and should solve your problem. I have newer versions of photoshop and lrc but they will not open a dng directly. That is what should have. You don't have to use the viewer if you don't want to. just being installed is enough.

Download DNG Viewer | Free Dng file viewer for Windows

DNG's can be opened by the Photos app, for example. XnView MP (free for personal use) can also do that.

Presently it happens that Photos is associated with DNGs and I see the thumbnail for the sample I downloaded.

It's possible that variants of DNGs are handled differently I suppose (e.g. your post #6) - hence my suggestion you upload one you're having problems with and provide a link to it.

Whilst it's easy enough for someone else to play with one file, it seems more likely it's the processing of a lot of large files that's the issue:

eventually (Hr+) they will turn into thumbnails

Some ideas here:
How to speed up loading thumbnails on Windows 10? — Auslogics Blog