Just post a raw file and have people sharpen it and try to guage it…sorry I didnt’ find the examples too useful for a proper comparison…too much was over contrasted and blown out to really assess sharpness…
Edit I see you have used Dropbox, sorry… but you dont’ need to you can just upload them…
Diffuse and sharpen is a very interesting (and powerful) tool. My previous laptop would also struggle with applying it, particularly if I mistyped a number in one of the dialogs. For iterations, I’ve found no value in numbers greater than about 4 or 5 and often stick to a 3.
I’d suggest you try it.
I also see that in the comparisons, the DT image is a little darker than the other 2. I’m uncertain what you mean by “pixel peeping at ridiculous levels” - does this mean the images you posted are crops at more than 100%?
I am by no means an expert at DT, but I tried a few settings and got a result that to my eye matched LR. I noted that I had to adjust colours to match those of LR/C1.
I’ve uploaded my sidecar file for you to try, and see what I did. I applied a little sharpening first, and then used the diffuse and sharpen module and zoomed in to check my work at up to 200%.
I hope it’s of value to you. But I’m open to further discussion on this - I’m sure I’ll learn something from it.
Cheers,
Michael P.
DSC04669.ARW.xmp (7.3 KB)
Does this mean you’re using the Sharpen module? IMHO that’s the worst one. Try some of the presets of diffuse or sharpen, I haven’t found the need to tweak them, but that’s down to personal preference and equipment.
Diffuse or Sharpen is definitely the way!
Think of it as a layered process, from the bottom up it should be going from coarse to fine details. I would suggest (as others have), to use the following presets
dehaze → lens deblur → sharpening demosaicing
It will probably be more sharp then it needs to be (I rarely use all three with full effect - actually I have my own presets, which are adapted to my taste), so they can be tuned down a bit (lower iterations/lower speed/higher edge threshold).
If this all fails, you might try the contrast equalizer on top.
As a sidenote, at the beginning of my darktable career I also struggelt with sharpness in comparison to lightroom. But using the modules as described, I don’t have this issue anymore. Pictures are now plenty sharp (if I need that, what I actually don’t do most times!).
P.S. In some pictures it can be beneficial, to change the demosaicing algorithm. I find ‘amaze+vng’ 0.35 gives often a good result. But try for yourself. I’m seeing improvements in fine details of bird feathers or forest leaves in the distance, …
You can also try the highpass module. See darktable 4.2 user manual - highpass.
Also, don’t forget that if you process raw images, darktable gives you an option to mask based on input detail level. You could avoid increasing noise in flat areas, and concentrate on edges and areas rich in details. See ‘details threshold’ at darktable 4.2 user manual - mask refinement & additional controls.
With diffuse or sharpen, you can use the presets marked here (I own old cameras that have anti-aliasing filters):
1st (bottom) instance is local contrast, 2nd is the sharpen demosaicing. Very rarely, I use the lens deblur presets, too (usually masked).
To be honest, I’ve never really worried to much about sharpness at these levels, so I might not be the best to answer. I don’t have a camera with such a high resolution either… 
Having said that, I was a little surprised that I could not get a match to your Lr version using diffuse and sharpen.
I recently upgraded to a GTX1650 and D&S is quite snappy (relatively). I still don’t fully understand how to fine tune D&S to be honest, but I’m usually very satisfied with the presets.
Anyway, I settled for using D&S set to the sharpen demosaicing (no AA filter) preset, which doesn’t tax the system much either, then I used contrast eq for the rest. I think this looks ok.
DSC04669.ARW.xmp (10.7 KB)
Interesting topic - I don’t know what kind of algorithm Lr uses for sharpening.
Hmmm. that doesn’t look quite as sharp as I wanted. Here’s another one with a second instance of contrast eq. It might seem a bother, but if you actually wanted this it would be easy to make a style that applies as many sharpening modules as wanted in one click.
DSC04669.ARW-01.xmp (11.6 KB)
I’m running a recent dt 4.3 - just in case my .xmp doesn’t work, my contrast eq looks like this:
and this:
The C1 images also are more contrasty, which increases the perception of sharpness. (See, for example, Still need 'sharpen' module after D&S ? - #14 by rvietor).
In the bottom image, the middle one (from C1) looks horribly oversharpend to me when viewed 1:1.
This discussion is so useful. Thanks everyone!
Only as a small addition a simplified diagram about two important controllers at diffuse and sharpen module with which one - in contrast to other modules for sharpening - can hold the artifacts very well in check:
As some one mentioned you can use the details threshold setting of masking and really dial in the sharpening so that you can be far more aggressive if that is your choice… then you can then make it as crispy as you like to the point that your image looks like it is dehydrating… 
Sharpness wise I was never really happy with my A7III files in DT until the diffuse or sharpen module, just the aa filter preset gives the perfect starting point. I can then use more instances with different presets or use local contrast and contrast equaliser to get the results I’m after, which most of the time would be sharp but not over sharp.
Have you ever tested this “hypothesis of being faster”? “Someone” is claiming so be removing things but on the other side no dt stuff that really helps here a lot (especially on master) has been ported.
Just playing around now with some of my images because my monitor came with three months of Adobe CC and I’ve got the free version of C1. LR over does the sharpening imo, I’m having to tone that and the contrast down. C1 over does it as well but it looks better and not as much toning down needed.
Another thing to keep in mind is that DT does not sharpen after resize when exporing, which means that exported JPEGs may lose a bit of sharpness compared to what is shown in the darkroom. There’s a Lua script to sharpen on export but I haven’t had time to test it yet.
I have not tested the speed difference, but on my computer sometimes DT crashes when I engage astrophoto denoise. I believe this is a problem with my computer rather than a DT problem. However, editing the same image in Ansel when this occurs allows me to apply astrophoto denoise without a crash. That is why I suggested Andy the OP might want to try the fork.
BTW, having tried Ansel there is much I miss from DT. I personally use shadow and highlights module a lot. Lets be fair, this module or its equivalent is probably in every piece of commercial software and even FOSS. It is there for a reason. It works well. Then AP comes along and tells as it is bad. Well as much as I like the tone equalizer module and use it, the look is different to shadows and highlights. I really appreciate all the great work that AP has done, but I don’t want to be forced to do it his way and only his way.
In Ansel I also I miss the export module in darkroom view. I do not to have to go back to lightroom view to check or set my export settings. I also love the way DT now names the processing module with the preset used.
As much as I dislike his communication style, he clearly articulated the problems with this module and said its fine as long as you don’t push it hard.
I totally agree with this statement. He also said photography is about the look. So if it looks good it is good.
What I really like about DT’s shadow and highlights module is the ability to soften with bilateral filter if halo effects occur. It is also better to perform multiple instances of smaller values than one large sledgehammer adjustment.
I am working a playraw image at the moment and the dynamic range of the lighting means I am using both the tone equalizer module and the shadow and highlights module.
Terry, thanks for reminding me about this issue. Will try to get this fixed asap There are already to reported issue at github about this.
