W10 issue with DNG files


Mar 8, 2014
Wales, UK
Lightroom Experience
Lightroom Version
Lightroom Version Number
Lightroom version: 6.14 [ 1149743 ] perpetual
Operating System
  1. Windows 10
Not specifically LR, but as my DNG photo are for LR, there may be someone here who knows how to resolve the problem.
If I go to a folder - all of jpeg files with have a thumbnail
Very few DNG files will have a thumbnail (often 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
I have no trouble displaying DNG images in Windows Explorer. No special CODEC installed. How did you create the DNGs?

You say that "very few" DNGs have a thumbnail. That indicates that there is a difference between those files and those which have no thumbnail.
Some have thumbnails some don’t.
from my camera they are converted using Adobe RAW conversion utility, from my phone straight in as DNG files.
as an example opened a folder and zero DNG files had thumbnails …. After leaving window open and active, after about 40mins a couple of files changed to have thumbnails.
some go to a purple solid colour first before changing to a thumbnail.
All will open by MS picture viewer if double clicked …but can take 20 to 30 sec for a DNG to open.
My phone creates DNG files direct .. my camera has to have file converted using Adobe DNG converter.
Just did a test and showed something I had not realised before.
File saved to Desktop ..... and it has the correct thumbnail.

When I move file to a sub-folder of My_Pictures is arrives there without a thumbnail.
LR identifies the RAW file whether on desktop or in a my_pictures folder

Noticed another anomaly .... on my phone the selection is simply to output 'RAW' files.
They arrive on PC as filename.DNG
I just opened file with Mediainfo and it reports it as an invalid tiff ? (see attached)


  • file info.jpg
    file info.jpg
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I deleted the Thumbnail cache, increased its size to 4MB and rebuilt ..... still the same ... here is a typical folder, originally (after new cache) all were icons, very quickly jpeg changed to a thumbnail.
Some of DG changed to solid block of colour (see pic) rest stayed as default icon.

contents 2.jpg
As another test took a pic with camera ... it saves in RW2 format (Lumix)
Media info advises little:
Complete name : C:\Users\Rick\Desktop\P1001487.RW2
File size : 23.1 MiB

I use the Adobe RAW file converter and it turns it into a DNG file.
Media Info advises:

Complete name : C:\Users\Rick\Desktop\0102P1001487.dng
Format : TIFF
File size : 18.7 MiB
Writing application : Panasonic Adobe DNG Converter 11.3 (Windows)
Writing library : DC-GX9
FileExtension_Invalid : tiff tif

Format : Raw
Format settings : Little
Width : 256 pixels
Height : 192 pixels
Color space : RGB
Bit depth : 8 bits
Compression mode : Lossless
Encoded date : 2024:02:01 14:14:23

So here is the anomaly .... an original DNG file is tagged as FileExtension_Invalid: tiff tif
A converted RW2 file to DNG is also tagged as FileExtension_Invalid: tiff tif

The converted file on desktop had no thumbnail, but when I double clicked to view, it then created a Thumbnail.
However when I move it to a sub folder of 'My_Pictures' it once again has no Thumbnail.

This is the file from desktop
As DNG files have Thumbnail OK on desktop ... but removed when moved to subfolder in My Pictures .... could it be the folder attributes for 'My Pictures' are not optimal to allow DNG
The DNG files without thumbnails import happily into LR and appear as normal.

As part of testing, I copied DNG files to a USB drive to test on another PC. I copied both files with and without thumbnails.
Interesting observation
The files without thumbnails brought up the following error :

USB file error.jpg