I raised this on LR Classic forum, trying here as some suggested similar issues have been rsolved here.
Windows 10 and LR Lightroom version: 6.14 [ 1149743 ]
If I go to a Windows 10 folder - all of the jpeg files with have a thumbnail (as do png, tiff etc)
Very few DNG files will have a thumbnail (usually none)
I have installed Microsoft raw image Extension .... v3 no difference
Have followed the steps to kill thumbnail cache, delete it, and restart explorer ... all jpeg thumbnails rebuild (slowly) but not DNG.
Have also followed the tip to uncheck 'always shows icons, never thumbnails'T in folder prefernces.
I have found an intesreting anomaly ...
My phone creates DNG files directly .. my camera has to have the raw files converted and I use ADOBE DNG converter to do that.
A test showed something I had not realised before.
Files saved to Desktop ..... the native DNG has the correct thumbnail, the converted file doesn't, but if I double click on it, a thumbnail is then created.
When I move files to a sub-folder of 'Pictures' is arrives there without a thumbnail.
However when I move it to a sub folder of 'Pictures' it once again has no Thumbnail.
LR identifies and can use the RAW file whether on desktop or in a my_pictures folder.
An native DNG file in properties is tagged as FileExtension_Invalid: tiff tif
A converted RW2 file to DNG is also tagged as FileExtension_Invalid: tiff tif
I tried delaing with Microsoft but they say as issue is with Adobe Raw Converter files they defer to Adobe
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