Embedded JPEG of CR3 not displayed for larger thumbnails in lighttable

Software darktable
1

It seems that the embedded jpg of Canon CR3 files is not displayed in lighttable for larger thumbnails; instead the processed raw is displayed even if it has never been opened in darkroom (in Preferences\Lighttable I’ve set ‘use raw file instead of embedded jpeg from size’ to ‘never’).
For both of my cameras producing CR3s this is the case but not for the CR2 files. I observed that in various layouts (zoomable, culling), dt 4.0.1 on Windows 10.

In the following example I have duplicated the image and opened the one on the right in darkroom to set Preserve chrominance to ‘No’ in filmic. The one on the left has not been opened in darkroom. See difference in brightness and the clipped highlights on the trunk.

screenshots from small

small thumbs
small thumbs1698×863 522 KB

and larger thumbnail

large thumbs
large thumbs2264×1143 899 KB

2

The doc?

image
image713×44 5.01 KB

3

https://docs.darktable.org/usermanual/development/en/preferences-settings/lighttable/#thumbnails

4

I tried all options there from always to never, closing dt in between, but still the same behavior. But as said, I don’t observe that for CR2s.

Here’s an example file
BF8I1989.CR3 (22.1 MB)

5

I vaguely remember exiv2 maybe having a limit on supported thumbnail size to prevent DoS and such, so maybe you’re hitting this?

$ exiv2 -pp BF8I1989.CR3
Preview 1: image/jpeg, 160x120 pixels, 14121 bytes
Preview 2: image/jpeg, 1620x1080 pixels, 371587 bytes
6

Actually, exiv2 -ep BF8I1989.CR3 has no problems extracting these (w/ Windows MSYS2 exiv2 0.27.5 package), so there might be something else going on…

7

It’s not really a big deal and it doesn’t slow down the review in lighttable by much. I just stumbled over it when culling through new images and observing the reconstructed highlights. But you also cannot compare your edit with the camera jpeg if you are interested in that.