Thumbnail corruption of some DNG files

[robbo56gbr]

I will explain the scenario where I came to see the above topic.
I have Canon R5 Mk2 and shoot Raw (CR3). I used darktable as my raw editor, currently it does not recognise these CR3s as they have not yet supported it.

To get around this I use Adobe DNG convertor to create DNG copies of my CR3 raws. These DNGs are buddy files to my raws in iMatch.  All the files in a batch convert with no error.  I can view these DNGs in Windows File explorer ( Windows I think just displays the embedded jpeg as the resolution has shrunk)

Also to note Darktable can happily see and edit all the DNGs without a problem

However when the DNGs are imported to Imatch, usually at least one or 2 in a batch of up to 100 will have their thumbnail corrupted with horizontal banding like a sliced up image.  At first I thought the DNG itself was corrupted but I have proved this is not the case.  I also just discovered that by a Forced update Shift Ctrl F5, the thumbnails come back corrected.

So ultimately no problem, but I wonder what may be causing this.  It is repeatable

Thanks

[Mario]

Are you using WIC or LibRaw with IMatch?

[robbo56gbr]

I am using WIC

[Mario]

Try LibRaw. Edit menu > Preferences > Application. Search for photools and enable "Prefer photools.com RAW Processing".

IMatch 2025 uses the official Adobe DNG software toolkit and combines it with LibRRaw to support all of the latest DNG flavors, including JPGXL. I'm not sure of the Windows WIC DNG codec is up-to-date. Only Microsoft can know that.

[robbo56gbr]

From your comments above on LibRaw I am wondering when it would be better (if ever) to use WIC. thanks

[Mario]

LibRaw / photools.com RAW processing is the default since IMatch 2025. No camera vendor provides WIC codecs anymore, or developer support. Microsoft seems to prioritize updates to their WIC codecs very low, as it seems. Wasting time with nonsense like Recall instead...