How to add modules to the overlay image in Composite?

[finestructure]

I have two photos that I want to stitch, due to a different subject being in focus in each photo. I need to match the backgrounds, which have a different degree of blur. I overlaid the sharp one over the blurred one. According to the documentation, I can apply modules to the sharp photo as long as they are before “Composite” in the pipeline. This doesn’t work. Some modules can have an effect, but “Diffuse or Sharpen” or “Blur” don’t do anything. Can I make this work or is there a rule that refuses to execute certain modules in an overlaid image?

The workaround is to reverse the order and apply DorS on the bottom image instead with a mask (reusing the gradient from the composite module).

This is the result with no blur in the overlay. You can see the diagonal line going down the center of the image:

I release these images under the CC BY SA license.
SIU02545.ARW (24.2 MB)
SIU02545.ARW.xmp (17.7 KB)
SIU02550.ARW (24.4 MB)
SIU02550.ARW.xmp (13.5 KB)

[deekay]

I think it depends on the position of the composite module in the pixelpipe of the base image. If it is before the DorS module (no matter if that is active or not in the base image), then for the overlayed image the pixelpipe is also only processed up to that position.

[gwbarn]

I’ve had a look; I’ve never used Composite myself but I have seen some of Nicolas’ videos that cover it (https://www.youtube.com/watch?v=OF7ZcDPQfeM). You need the module active and before composite in BOTH images.

[finestructure]

Thank you both! If I can confirm that behavior, I’ll read over the docs again and see if that fact could use clarification.

And it’s good to be introduced to a new darktable tutorial creator that the algorithm never saw fit to show me!