Colour preview shown instead of monochrome for 3 of the 4 aspect ratios (DC-LX100M2)

[jade-nl]

Is there an existing issue for this?

• I checked and did not find my issue in the already reported ones

Describe the bug

When shooting in monochrome mode with a Panasonic DC-LX100M2, the full preview shown in lighttable (using W, Ctrl-W or F) show a colour preview for 3 of the 4 aspect ratios. 1:1 is the only one that is shown correctly in monochrome.

Steps to reproduce

• switch this camera to one of the monochrome modes,
• shoot images in all 4 aspect ratios that this camera supports,
• load these 4 images into lighttable
• check/set: preferences -> processing -> detect monochrome previews
• thumbnails in lighttable are shown in monochrome (as expected),
• select one of the 4 images and press W (ctrl-W)
• cycle through all 4 and notice that only the square one is shown in monochrome.

Expected behavior

all aspect ratios should be shown in monochrome when images are shot in monochrome

Logfile | Screenshot | Screencast

panasonic.ratios.bw.mp4

The first part of the video shows me selecting each image and pressing W, the second part shows me having pressed F and use the arrow keys to cycle.

Commit

No response

Where did you obtain darktable from?

darktable.org / GitHub release

darktable version

all versions, self compiled and flatpak

What OS are you using?

Linux

What is the version of your OS?

debian

Describe your system

• not relevant -

Are you using OpenCL GPU in darktable?

None

If yes, what is the GPU card and driver?

• not relevant -

Please provide additional context if applicable. You can attach files too, but might need to rename to .txt or .zip

I'm assuming that one doesn't have examples lying around to use for debugging, here are the four monochrome images from the video (rename them to rw2)":

3:2
P1002591.txt

16:9
P1002592.txt

1:1
P1002593.txt

4:3
P1002594.txt

Not sure if this is a general Panasonic issue or specific to the DC-LX100M2.

[MStraeten]

please share your ~/.config/darktablerc - maybe the preview is generated from raw depending on the sizes according to the settings.
If the preview is generated from raw then the mode used to generate the embedded preview is ignored

[jade-nl]

All my darktablerc files? I see this behaviour in 4.2, 5.0.1, 5.2 and 5.3 dev. Most are from clean installs (no files present when first started).

Maybe tell me which entries you're interested in?

Also: I do not see this behaviour with my Z6ii, which also has 4 aspect ratios I regularly use.

[ralfbrown]

There is a setting thumbnail_raw_min_level which controls the maximum size for which a preview uses the embedded JPEG generated by the camera. While this defaults to "never" (i.e. always use the JPEG) at least in recent versions, if the on-screen resolution is greater than the resolution of the embedded JPEG, darktable will still process the raw data to generate the preview. Depending on the aspect ratio of the available area for the preview, only the 1:1 preview may be small enough to use the embedded JPEG.

Try shrinking the darktable window by 25% and check whether the behavior changes. If it does, the above explanation is the answer.

[ralfbrown]

The embedded JPEG for the 1:1 image is only 1920x1920, while the full raw data is 3568x3568....

[jade-nl]

That entry is set to:

plugins/lighttable/thumbnail_raw_min_level=never

Try shrinking the darktable window by 25% and check whether the behavior changes. If it does, the above explanation is the answer.

Yep, significantly resizing the window keeps the preview monochrone. But that's not a solution.

I deliberately chose to show the embedded jpg because then, among other things, I get to see the monochrome version. I therefore expect a full-screen preview to be monochrome as well, so I can see the details.

[jade-nl]

Just a clarification about my previous reply:

When I say I expect a full screen monochrome preview I do not mean that the image should be blown-up to my monitor size or the max RAW size (whatever comes first).

If the embedded jpg is smaller then the raw/monitor I do expect to see that smaller jpg. In this case a 1920x1080 / 1920x1280 / 1920x1440 / 1920x1920 monochrome preview.

I'm not sure why that would not be possible.

[jenshannoschwalm]

You can 1) let dt check if the raw was shot in monochrome while importing 2) use specific auto-applied presets for raw monochromes and 3) always generate thumbs from raw.

That's my very simple initial workflow and it has been working fine "for ages".

[jade-nl]

@jenshannoschwalm

Bit of a strange answer to be honest.

Point 1, let darktable check if raw is monochrome: check! And this does not function in combination with preview shown in lighttable, as very clearly stated in my original reply.

I'm in lighttable view and assessing all the imported monochrome files, which includes showing them full screen at times to be able to better assess them.

What is the point of having a lighttable view that can only be partially used to view, manage and cull?

As mentioned in my previous reply: Why is it not possible to just show the largest embedded preview?

Point 2 is irrelevant and darkroom specific.

Point 3 will make it so that i see coloured thumbnails in lighttable view. How is that a solution if i want to see monochrome thumbnails and previews?

Please, don't confuse your workflow with mine.

[jenshannoschwalm]

Don't understand your issue at all i must confess.

1. Loading all images using detect monochrome previews as here

does exactly that what i said with all your provided raws, all all accepted as monochrome.

2. Your raws are simply not "monochrome" at all as you know.
3. What you see in lighttable is of course related to what we do in darkroom if your thumbs are processed from raw with auto presets applied.

Point 3 will make it so that i see coloured thumbnails in lighttable view

As i suggested above, you might define an auto-applied preset that is applied to all raws detected as monochrome, like this

and you will see b/w images.

If this doesn't fit because you always want to have the embedded thumbs visible before developing in darkroom why don't you select never ? I just tried and it works exactly as intended here.

[jade-nl]

@jenshannoschwalm

• First and foremost:

The underlying issue has already been established. Please re-read the replies by @ralfbrown and my reply to that.

This also indicates that this issue, at its core, has nothing to do with monochrome.

My opinion about this: if thumbnail_raw_min_level=never then darktable should never use the raw image and always show the embedded jpg, whatever the max size of the embedded jpg when using W, Ctrl-W or F in lighttable view. Never should actually mean never in this case.

• Secondly:

It is a complete mystery to me why you concluded that this might be a true monochrome issue. The title and my initial post, in text and video, clearly show that colour is being shown. Not to mention the already found underlying issue.

Maybe the title of this issue needs to be changed now that the underlying issue has been found. But I, not being a developer, am not at all certain what wording would clarify this issue more accurate. Feel free to change it.

[jenshannoschwalm]

Took some time to rethink about this. Technically the "issue" was clear immediately.

I am still not sure "if and how to fix correctly". Whatever the setting for "get thumb mipmap from embedded" is, we might not have the requested size being available. Currently we fall back to "develop from raw" instead of upscaling (this is not mentioned in the manual). This is generally a good idea to avoid blurry or blocky thumbs/previews as provided embedded jpegs vary a lot depending on vendor/firmware. (as here in the 1:1 raw file)

Here we have a cornercase. It's neither good to enforce "check for mono" for performance reasons nor always upscale because of inferior quality.

I would suggest to leave the implementation "as is" and improve tooltip & manual

[jade-nl]

@jenshannoschwalm

Except for one thing, this sounds reasonable.

The thing I don't understand is why upscaling is needed at all. Why can't the available embedded jpeg be shown without upscaling? Isn't this, a possible small(er) full preview, a direct result of choosing thumbnail_raw_min_level=never and thus a user choice?

Anyway, I'm not a developer and might simplify things way too much :-) This might indeed be a corner case. If I look at all my previous cameras (11 in total, mostly Nikons), which is a rather small data point, I only see this with this one specific Panasonic.

OK, if most agree with the "as is" solution you can close this one after the docs are updated.

[jenshannoschwalm]

... why upscaling is needed at all.

There is no garantee that the raw file provides an embedded jpg at all or something decent (your problematic raw would count for me), what if there is just a thumb of 600x400 pix on a 4k monitor? Keep as is? Really?

If I look at all my previous cameras

Some people do crazy things with dng converters and that's happening more & more often.

OK, if most agree with the "as is" solution you can close this one after the docs are updated.

That would be something you can contribute :-) That's how people get/got involved, something itches so get into it :-)