I’ve downloaded PR6 trial, checked sample ‘High Fidelity’ DNG output from Nikon Z8 raw NEF (losslessly compressed) with exiftool. Quick and dirty investigations show that it’s purely Microsoft problem and I don’t see anything strange about DxO DNG packaging.
The main full-resolution 8256 x 5504 subfile of the PR6 ‘High Fidelity’ DNG (which is a TIFF with DNG-specific tags included) has the following key tags:
- SamplesPerPixel : 3
- BitsPerSample : 16 16 16
- Compression : JPEG XL (52546)
- PhotometricInterpretation : Linear Raw (34892)
So it’s JPEG XL compression for the main image data indeed.
The other two subfiles inside the DNG are:
- thumbnail, 258 x 172 pixels, uncompressed 8-bit RGB, 133,344 bytes
- preview image, 8256 x 5504 pixels, like the original raw, JPEG compression with PhotometricInterpretation = YCbCr, YCbCrSubSampling = YCbCr4:4:4 (1 1), 8,339,194 bytes.
To address @IanS post above, the preview image is a perfectly standard JPG file, with JFIF header, standard JPEG compression/encoding and so on. You can extract it using “exiftool -b -PreviewImage” and display it using Windows Photos app without any problems. I’m not sure why Windows Photos doesn’t display at least this preview image, when trying to display the DNG containing it and JPEG XL extension missing – the code for that is missing.
BTW, the “-JpgFromRaw” exiftool option doesn’t work, probably because it doesn’t consider linear DNG to be RAW.
Some background info: The original NEF was 61MB (45mpx, 14-bit losslessly compressed, shot at ISO 12k), while PR6.0 ‘High Fidelity’ linear raw DNG was 37MB in size, with the 8MB JPG full-resolution preview and a small thumbnail inside.