RawTerapee 16Bit & 32Bit Floating export suddenly creating washed out thumbnails

I use Window 11. Canon R6 (CR3 RAW files). I want the metadata from them, so I convert them
to Adobe DNGs. (Compatibility camera Raw 14 or later.)
Then I edit these DNGs in RawTherapee.
I’ve been doing it this way for a year or two, and exporting/saving them ok.
Suddenly, when I save in 16 Bit or 32 Bit FLOATING TIFFS the thumbnails look washed out in W11 file explorer. But if I export in 16 Bit TIFF (non Floating) the thumbnails are OK. However, the washed out ones then open OK in GIMP, but are washed out if I open them in W11 Photos viewer.
I updated ACR recently, but changed the settings back to camera Raw 14. I also uninstalled RawTherapee, plus all the folders, (cache,profilesetc) from the RT folder and reinstalled it. But still get washed out W11 thumbnails.
Anyone got an idea what’s going on here?

This is not RT’s problem, and not sudden. The same would happen if you export from darktable or GIMP… It looks like Windows (and it’s apps) assume a linear colour profile (or no colour profile) when they run into floating point data.

Ah. Thanks kmilos. That’s interesting. I read somewhere to use 32-bit floating Tiffs (RawPedia ??) and recently changed to saving them as such. I’ll go back to 16-bit Int. I’m happy it wasn’t me changing some setting or other that I wasn’t aware of.

That was not to say you shouldn’t use floating point - that depends on your needs only - just don’t mind what Windows shows.


I just downloaded the 5.1 rc1 and exported a file to 32bit floating tiff… as you say the thumbs were washed out but in Win11 viewer it opens for a fraction of a second washed out and then its correct…

In Irfanview it is washed out and in XNview its better but not displayed correctly with areas that look gamut challenged…