Darktable does not import X and Y Resolution tags

Software darktable
1

I digitalized some old photos in DNG format for archival purposes, with the intention to use Darktable to further post-processing them.
However, “X Resolution” and “Y Resolution” tags are not present in the imported images.
As a result, when exporting their post-processed version, the resolution tags are arbitrarily set to 300 (being the original value much higher).
Since resolution and size represent the real size of the original picture, I would like to preserve this value.
I am using darktable 4.6.1 on Ubuntu 22.04.
Did I miss some import settings?

Edit: I used an Epson Perfection V550 Photo and VueScan 9 x64 (9.8.26.08).

2

What software and hardware created these dngs?

3

I used an Epson Perfection V550 Photo and VueScan 9 x64 (9.8.26.08).
(I also reported these info in the original post)

4

Can you share the group tag?

5

I am not sure about your question.
Using exiftool, the group name of the tags is:
[EXIF] X Resolution : 6400
[EXIF] Y Resolution : 6400

I cannot provide the image because of its size.
But if it helps, I can scan a small portion, resulting in an image of a
reasonable size.

6

I dont think dt reads those tags. I’m not sure of the value for them. It seems like they mean the pixels per inch (mm). darktable exports the image size (width/height) in pixels.

7

The unit of measure is given in a separate tag
[EXIF] Resolution Unit : inches

I also suppose that DT does not consider this feature.
It is meaningless, for a picture captured by a camera, at least until you need to print it.
However, resolution carries information about the original, in case of scanning.
It is curious that it provide these tags when exporting the image (again, probably because the printing becomes the next step).

8

This is because these tags are mandatory according to the TIFF/EP spec. Although Exif spec says those are optional w/ 72dpi as default, 300dpi is as good as value as any, given that the print size is usually not known a priori at export time.

However, you might have an interesting use case here.