DNG 'unsupported format variant' with Silverfast negative scan

[tilmann]

I started using the HDR raw DNG file format (48-bit) to archive negative scans coming out of Silverfast. Mylio and Affinity Photo can read and display these files without a problem. In PM (Build 5820) the thumbnail displays are empty and the filenames are shown in red. When opening in the Preview window, it shows 'Unsupported Format Variant' instead of the preview.
Interestingly, in cases where I created the corresponding JPEG file in the same folder, PM does not render the JPEG either, although it recognizes the JPEG's presence by showing 'filename.png+jpg' below the thumbnail. Also, trying to add IPTC information to the files results in an error message.
I enabled Raw Rendering with Adobe DNG Converter, but when trying to use Tools/Raw-to-DNG I get an error message that no raw files are available.
When manually processing the Silverfast DNG files with Adobe DNG converter, PM can read the files. However, when I developed the converted, PM readable files I noticed that the color information must have been changed during the conversion process and the color rendering comes out quite differently in my raw developer. Also, Adobe DNG converter reduces the file size to about 50% of the original (despite using a non-compressed setting). Since the file content appears to be modified during the DNG conversion, I would prefer to stick with the original DNG images in my archive.
Any suggestions how to make these Silverfast DNG files usable in PM, especially for using the IPTC functionality?
Thanks,
Tilmann

[tilmann]

Two additional pieces of information, in case they could be helpful:
1. The DNG 'unsupported format variant' issue occurs with both the Mac and Windows versions of PM
2. When separating the view of DNG and JPEG thumbnails, the JPEG thumbnail will be displayed by PM, so it is not an issue with the rendering of the JPEG file.
Thanks again for looking into this.

[Kirk Baker]

Two additional pieces of information, in case they could be helpful:
1. The DNG 'unsupported format variant' issue occurs with both the Mac and Windows versions of PM
2. When separating the view of DNG and JPEG thumbnails, the JPEG thumbnail will be displayed by PM, so it is not an issue with the rendering of the JPEG file.
Thanks again for looking into this.

Is there some way you can share one of your DNG files with us?

-Kirk

[tilmann]

Kirk,
I just sent you a DM with a link to download a couple of examples (color and bw).
Thanks much in advance.
-Tilmann

[Kirk Baker]

Tilmann,

I just sent you a DM with a link to download a couple of examples (color and bw).

Got it, thanks.

-Kirk

[tilmann]

Hi Kirk,
just checking in to see if you had a chance to look at the DNG files.
Thanks much in advance.
-Tilmann

[Kirk Baker]

Tilmann,

I just did, finally.  The DNG files you sent have no previews or thumbnails in them whatsoever.  Photo Mechanic cannot handle DNG files that have no non-RAW image data.  You'll either have to adjust the settings in the scanner software (if it has them) or run them through the Adobe DNG Converter to produce DNG files with previews (high resolution preferred.)

-Kirk

[tilmann]

Thanks, Kirk, for looking into the files.
I understand that PM cannot display the files without a thumbnail or preview. Make total sense.

If the file structure is otherwise in compliance with the DNG format (which I would hope), could you modify the handling of these files by PM in a way that it can add IPTC information or write a sidecar file? Since I use PM primarily for ingestion and/or adding IPTC info in my workflow, it would great if PM would write IPTC data to these files or just create an XMP sidecar, even if not displaying a thumbnail.

Thanks again,
Tilmann

[Kirk Baker]

Tilmann,

Thanks, Kirk, for looking into the files.
I understand that PM cannot display the files without a thumbnail or preview. Make total sense.

If the file structure is otherwise in compliance with the DNG format (which I would hope), could you modify the handling of these files by PM in a way that it can add IPTC information or write a sidecar file? Since I use PM primarily for ingestion and/or adding IPTC info in my workflow, it would great if PM would write IPTC data to these files or just create an XMP sidecar, even if not displaying a thumbnail.

Probably not, no.  Since it has no thumbnail or preview, it's not considered a valid DNG file at all by Photo Mechanic.

-Kirk