Fixing Foveon DNGs in darktable

The short version

I have written a little plugin that makes it possible to use DNGs produced by Sigma Quattro cameras with #darktable without having to fix white balance and color calibration on each and every image. You can download it

here

Installation instructions:

Unzip the file, copy it into your ~/.config/darktable/lua/contrib folder and activate it from the “start/stop scripts” menu in darktable.

The slightly longer version

As readers of this blog are probably aware by now, there is a bug in darktable which leads to images captured with a Foveon-Quattro equipped Sigma camera to be displayed with the wrong colours.

The effect can be fixed with some manual fiddling, but it’s a major nuisance.

The bug has been described in length here and here so there’s no point repeating it all again here.

Now I have to admit after one year I grew a little inpatient last week and regrettably said a few things that are not really helpful.

After this had been pointed out to me, I decided to try and tackle the problem myself.

There is no way I could immerse myself into the depths of darktable programming in addition to all the other stuff I have going on at the moment, but at least I found the time to write a little lua plugin which provides a workaround.

For the technically minded: The plugin works by disabling color calibration and resetting white balance to “as shot” upon first loading a Sigma Foveon DNG image in the darkroom.

This fix is applied only once, i.e., you’re free to adjust the white balance
setting as you see fit without the plugin interfering on the next load.

Caveats

• since the fix is only applied when first loading the image into the darkroom view, the thumbnails are still wrong after importing. Only when the image is first loaded in the darkroom view the thumbnail gets fixed, too.
  There’s no way around this due to the way lua plugins and darktable functions
• The “color calibration” module can’t be used, as it needs to be bypassed for this fix to work

Thanks

Thanks to Bill Ferguson for helping me with the lua script.

Have fun!