Panasonic G9 and Darkable issues (White Balance, colours are off)

[dmoltis (Davide)]

Hello everyone, first post here

I am a keen DarkTable user, I have been using it for over 5 years. Recently, however, I bought a Panasonic G9 and ever since I struggled with DarkTable.

Firstly, images look very dark and I need to apply between 1 and 2 EV almost always to get to a decent starting point. I know this has been discussed countless times, and I don’t want to start another lengthy discussion about filmic, scene-referred workflow, etc. I can live with this issue.

However, when it comes to white balance and colour rendition, I really struggle to get decent pictures. I’m going to show an example below.

DarkTable output

Unedited

This is how the picture comes after the standard pre-processing applied by default with the scene-referred workflow. Very dull, let’s fix exposure and black/white points with filmic now.

Tone adjustments, default white balance, colour calibration (invalid illuminant)

This was a quick edit where I only touched the exposure and filmic module. White balance and colour calibration were not touched. White balance was set to camera reference, whereas colour calibration’s illuminant was invalid. This is probably why colours are so off, with a sort of magenta cast.

It’s odd that DarkTable didn’t manage to get the right illuminant, but let’s fix that. Let’s set the illuminant to daylight

Tone adjustments, default white balance, colour calibration (daylight illuminant)

It looks a bit better now, but still not good in my opinion. Let’s now try to use the camera’s white balances

Tone adjustments, white balance as shot, colour calibration (same as pipeline, D50)

(can’t upload more than 4 pictures since I’m a new user, imagine a similar picture here )

Here I set the colour calibration illuminant to same as pipeline d50) and white balance as shot. This looks a tiny bit better, but in general I’m not pleased with the results. Finally, for a reference, here is how RawTherapee processes the image by default (I only applied the dynamic range compression, with default values)

RawTherapee default output (with dynamic range compression)

I would still tweak the image a bit, but I’m very pleased with RawTherapee’s default processing, it is much closer to the original scene and the camera’s JPEG.

Discussion

Now, I’m aware RawTherapee does a lot more than DarkTable by default. I know DarkTable’s philosophy is different in that it lets the user be in control. I like that, but the problem is that more often than not the starting point for me is abysmal. Sure, I can calibrate the white balance and do the necessary edits to make DarkTable’s colours look the way I want, but imagine having to adjust the white balance for every single image. It just makes editing not fun for me.

To me, there’s clearly something wrong between Panasonic and Darktable. Before the G9, I had a Canon 5D classic and I didn’t have such big issues with colours. I also tried to tweak input colours, demosaic algorithms and whatnot, I almost always get bad colours at the start.

Does anybody have the same problem? I played a little bit with RawTherapee re-editing a few pictures. I was blown away by how different the outputs are. RawTherapee’s default are pretty much spot-on, whereas DarkTable gives me a hard time even with a lot of processing.

Important note. I face this problem especially in daylight scenes or scenes with a warm light source. Colder scenes suffer much less from this issue.

Thanks for reading!

[paperdigits (Mica)]

Hey! Welcome!

Things will be a lot easier if you post a problematic raw file. We can talk about it in abstract a lot, but getting other people’s XMP files will be super helpful.

What a file looks like when first opened with the default processing is not very relevant, as it is acknowledged that you should make a style to apply by default.

If you’re having to add 2+ EV, check your camera’s metering mode and make some adjustment, as you’re missing the exposure.

The colors from both RT and DT look off, DT is too mangent, but RT looks too yellow. Do you have a problematic file that has sowmthing obviously white in it? Can you shoot a graycard when you’re out?

In DT, use the Color Balance RGB preset called Restore Basic Colorfulness and turn on local contrast. That should help.

[kofa (István Kovács)]

You may be affected by the black point issue - a fix for some Lumix cameras broke another bunch of Lumixes:
Panasonic S5: Underexposed images green/Black levels not read · Issue #9811 · darktable-org/darktable · GitHub vs
Lumix LX7 black point wrong · Issue #10008 · darktable-org/darktable · GitHub

See workaround here:

Panasonic TZ90 wb/colors

Also, the invalid indication in color calibration does not mean there is a problem; see https://docs.darktable.org/usermanual/3.6/module-reference/processing-modules/color-calibration/#cat-tab-workflow

When the CCT is followed by “(invalid)”, this means that the CCT figure is meaningless and wrong, because we are too far from either a daylight or a black body light spectrum. In this case, you are advised to use the custom illuminant. The chromatic adaptation will still perform as expected (see the note below), so the “(invalid)” tag only means that the current illuminant color is not accurately tied to the displayed CCT. This tag is nothing to be concerned about – it is merely there to tell you to stay away from the daylight and planckian illuminants because they will not behave as you might expect.

[dmoltis (Davide)]

Hi, thanks for your reply! I agree that neither DT nor RT look perfect, but RT is much closer to my liking, and at the very least it gets me much closer to the final picture.

Here is the raw and the corresponding xmp for the jpegs I uploaded here. The white t-shirt is pure white.

I think exposure in camera is fine as pictures look good in other software and in the camera.

I use the basic colourfulness preset in colour balance a lot, but the problem I’m concerned about here is the overall colour cast of DT, which is even accentuated with that preset

P1013143.RW2 (23.1 MB)
P1013143.RW2.xmp (8.6 KB)

[kofa (István Kovács)]

Cameras use a base curve that lifts midtones, so darker-than-jpg is quite natural. I simply have an auto-applied preset to add more exposure (1 EV) instead of darktable’s default (0.5 EV).
With raw black levels set to 143:

Default (as shot) WB in color calibration:

Sampling the in-shadow portion of the T-shirt:

Sampling the top of the T-shirt’s back:

[dmoltis (Davide)]

Wow, thanks a lot for this! I just tried myself and I can replicate your edits. I also checked the linked issues. I will create a preset for this while I wait for a fix. Thanks again!

[kofa (István Kovács)]

BTW, @s7habo (whose Youtube channel I highly recommend) often uses something like this as his color balance rgb starting point:

You may want to check out his latest videos, which are more tutorial-like than the previous, ‘short text + quick edit’ versions. https://www.youtube.com/user/s7habo/videos, parts 40-47 (contrast and colour in darktable).

[dmoltis (Davide)]

Cool videos, much appreciated!

[priort (Todd Prior)]

Also watch the video today in addition to the black point …if you have a calibrated monitor you may be able to improve your D65 WB coefficients and hence your resulting wb… See the first part of the video…

[EN] Make the most out of darktable color calibration features