Capture Sharpening - simply thank you 😊

Macchiato17 · July 27, 2025, 4:56pm

Wow… as @GMan mentioned a cool new feature here…

…just found that this PR has already been merged into master I played a little with it and it is really stunning to see this additional, subtle punch in sharpness it brings to the photo.

Thank you so much @hannoschwalm and Ingo Weyrich for this work. Awesome - and thanks for pushing darktable one step ahead again. It is so much fun to work with this wonderful piece of software Have a good time

Wilecoyote · July 27, 2025, 5:16pm

Yes, it is really an amazing addition and works very well!

g-man · July 27, 2025, 5:39pm

I’m on holidays, so I can’t test. This looks interesting too.

github.com/darktable-org/darktable

Dual demosaic for 5.4

master ← jenshannoschwalm:dual_demosaic_54

opened 06:56AM - 27 Jul 25 UTC

jenshannoschwalm

+307 -281

While working on capture sharpen i did a huge amount of pixel-peep-testing a lot… of images, low & high noise, xtrans and bayer looking for artefacts, moire handling and introduced maze patterns in low-contrast areas, thanks to many people sharing images with special problems btw. As a result of those tests i reimplemented dual demosaicing (@TurboGit so we have differences with integration tests) leading to an improved quality for low frequency content (better response for noisy signals, no color casts, no mazing). While doing so dual demosaicing performance has been improved quite a lot, it's performance now is only ~10-20% worse (instead of >50%) than it's main demosaicer and it uses less memory (important for tiling) both for CPU and OpenCL code paths. @da-phil @weltyj when working on capture i saw you both use dual demosaicing. Would you be able to test?

zurdo · July 27, 2025, 7:13pm

Yes a very nice new feature, thanks to the authors! And a nice example of crossf-ertilization between darktable and RawTherapee, if I followed the story correctly

hatsnp · July 27, 2025, 7:30pm

+1 . Many thanks to all those involved. I have given it a quick test and the results are very good. Probably the most natural looking “fine” sharpening in darktable at the moment.

kofa · July 27, 2025, 8:25pm

Just to make it clear, as there has been some confusion: Lars found out in the AgX thread that capture sharpening has been merged into master; however, agx itself is under review.

Thanks to @hannoschwalm for his continued great work!

clind · July 27, 2025, 9:10pm

Wow; wonderful news thanks @hannoschwalm for your work;

Soupy · July 28, 2025, 12:58am

Yes it’s great! Combining the subtleties of capture sharpening with the power of DoS is giving excellent results.

I’ve settled on a preset with 15 iterations, 1px radius, 0 edge sensitivity and 0.6px corner boost. Seems to work best on most images, but that is only tested with one camera / lens combo so far.

priort · July 28, 2025, 1:01am

How did you land there…I would guess the autocalculated one for the sensor was larger?? Was going smaller better… just curious…its new and deserves some experimenting…

Soupy · July 28, 2025, 1:19am

At first I didn’t realise the round button beside the slider was an auto button, so I manually adjusted, and found 1px to be the sweet spot. Much less seemed a bit soft, much more seemed a bit over cooked. I’ve tried on a variety of camera / lens combos now and notice the auto button typically gives between 0.6 and 0.8. The difference between that and 1px on many images is not greatly noticeable.

priort · July 28, 2025, 1:25am

Ya I have just played a little from the documentation the value is supposed to be calculated when you first add an iteration and I think it suggested zoomed out… I noticed that if I was at different zoom values the auto button gave a different result… I used some high radius with some restriction using the edge sensitivity which seems pretty much like the details threshold in the masking options…but as I said I really didn’t do much yet just some playing…I tried it on a recent play raw …the coffee shop shot in the downtown thread …you could really enhance the brick and mortar lines and these were good test points to look at as well as the small branches in the tree and leave at the top of the tree against the sky…

Tim · July 28, 2025, 1:32pm

What does “capture sharpening” mean?

kofa · July 28, 2025, 1:58pm

A sharpening mechanism ported from RawTherapee / ART, which is part of the demosaicking.
https://rawpedia.rawtherapee.com/Capture_Sharpening

kofa · July 28, 2025, 2:40pm

And the PR, including a ‘mini manual’:

github.com/darktable-org/darktable

Implement capture sharpening inside demosaic module

master ← jenshannoschwalm:demosaic_sharpen

opened 02:08PM - 01 Jun 25 UTC

jenshannoschwalm

+1569 -161

This has been discussed many times here and on pixls.us so here we go. As we hav…e D&S giving good results i was somewhat reluctant to work on this and do a pr but as CS works so good on RT and after a lot of testing (and using this on my personal images for a while with 3 auto applied presets for my fixed-lens camera - one for high-iso with CS turned off and two presets for wide open and "normal") i am pretty confident it's worth it and would be a significant improvement. (It took quite a while to spot a very bad bug in GPU code leading to system instability and crashes so unfortunately not for 5.2) Please test in depth and let's decide if this is for master. It's a lot of processing - so not a superfast module. _________________________________________________ Capture sharpening has been implemented to work inside the demosaic module so it's raw only. Credits to: Ingo Weyrich (heckflosse67@gmx.de), he implemented the original algorithm for rawtherapee, this implementation is based on his work, especially the convolution kernels. CPU and OpenCL code paths are both available. Demosaic module gets more parameters so there is a version bump. **The "mini manual"** (regularly updated to latest commit) Capture sharpening (CS) tries to recover details lost due to in-camera blurring, which can be caused by diffraction, the anti-aliasing filter or other sources of gaussian-type blur. Prerequisites are - good white balance parameters (same requirement as for highlights reconstruction or demosaic) - no chromatic aberration, you might want to add the "raw chromatic aberration" module - low noise as noise will be amplified by CS **Controls** 1. **capture sharpen** switches CS on if above zero and defines the strength of overall effect. CS works in an iterative process, this defines the number of iterations, mostly a setting of 10 will be enough. 2. **radius** defines the basic convolution gaussian sigma. This should not be set by "creative means" but to the blurring radius of the optical system and sensor, too large values will lead to artifacts like halos. Calculating a correct radius is provided internally. This will be done either if you a) click on the button besides the slider b) activate capture sharpen the first time after resetting to demosaic defaults or developing old edits. 3. **contrast threshold** As sensor noise will be amplified by CS we take some care about this by a per pixel variance analysis and use a logistic function with this threshold to avoid CS in noisy areas. The default is good for low iso images. Note the visualizing button at the right. 4. **corner boost** Increase the convolution radius in image corners outside the sharp centre. 5. **sharp centre** Define the "sharp" centre part of the image Note the visualizing button at the right.

kap55 · July 28, 2025, 6:52pm

I would just like to add my thanks to @hannoschwalm for this addition to the demosaic module. Deconvolution sharpening is something I became aware of several years ago through commercial software (which I no longer use) and always hoped it would eventually be introduced into darktable.