nice
Hmm, RT uses this kernel for sigma 0.5
0.0113437 0.0838195 0.0113437
0.0838195 0.6193470 0.0838195
0.0113437 0.0838195 0.0113437
D700_20090529_9255.NEF.xmp (10.5 KB)
I’ve used the base curve module in a way that it mimics exposure compensation with roll-off in the highlights before the real camera base curve.
I’ve then used the mystic golden spirales rules for the crop
In some edits, the gull has a dark or light halo. I haven’t looked at the raw file yet; maybe the light soft halo was there to begin with.
Look at the raw file. If there is some halo, it maybe is caused by shooting at F1.8
Way back when I implemented this, I took the example kernel from here:
http://setosa.io/ev/image-kernels/
and worked up the equation that yielded the ratio between the center nymber and the outliers. The code in rawproc:
Lord knows it’s probably wrong, fruits of bear-of-little-brain… 
Yes, I saw it in the background around the seagull’s head. I used a parametric mask on the background and reduced exposure there and it was gone
I just hard-coded this matrix in rawproc, and short-circuited the kernel constructor in favor of it. It blurs the image… 
Shouldn’t it? It’s a gaussian blur kernel.
Y’know, now that I recall, mine is not USM, which requires a blur. Mine is straight convolution sharpening…
My point was, that your kernel values were’nt exact enough for a sigma of 0.5
Ah, got it. Good thing I called it “strength” in the API… that could mean anything!
For 1.0, I’m probably going to add USM to the tool or replace what I have with it. Then, I’ll treat it as a proper sigma…
Edit: tie to the thread - that’s one sharp seagull you have there, @heckflosse
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Trouble is we can see where you did that by the reverse gradient, esp. where it ends at the nape… and it isn’t just you.
RT:
D700_20090529_9255_R.jpg.out.pp3 (11.7 KB)
Shokingly similar to @heckflosse’s with the slight difference that he just used a curve and I used a ton of stuff. So if you want to learn how to be ineffective…download my pp3 file. 
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Nice shot! I’ve gone for what is perhaps an illustrative, brighter and more saturated look while trying to keep things within the bounds of reason.
darktable 2.6.2: D700_20090529_9255_01.NEF.xmp (9.1 KB)
I couldn’t seem to get the tones I was after with base curve and/or tone curve, which I was using as I’m not yet confident with Filmic. But I switched to Filmic and things fell into place quickly after some slider dragging. 
I found that darktable’s Defringe module helped a lot with the chromatic aberration(?) around the gull. Before and after:
I applied another instance with stronger settings to the tail with a drawn, feathered mask to get rid of more unwanted green and magenta.
Equalizer with a mask to bring out feather detail in the breast and head. And I’m a sucker for Soften (with substantially reduced settings as compared to the defaults!), which I applied to the inverse of the same mask.
Spot white balance on the breast, giving a warmer feel, and some good ol’ Velvia.
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