[todd]

I had read some references about deconvolution sharpening before in regards to countering blur, specifically gaussian blur, but never connected any dots for an actual application. Then recently a fellow member tipped me off about using it as a diffraction correction technique in this post. Thanks to a handy tool in my raw converter of choice, Rawtherapee, I immediately went to experimenting with it, to many satisfying results... Since the issue/concern/factor of diffraction comes up quite frequently here on the board, I figured we should have a thread here about deconvolution sharpening, along with some examples...

The linked post above talks about using it in the context of large printing, where I am sure it also works wonders, but I've found that it also helps in web-sized improvements, and therefore should be helpful in any situation where diffraction is a concern. Personally I've been using it or at least trying it on whenever I'm working with a F13 or smaller image, using whatever intensity fits best to my eye and purpose (always viewing the effect/result at 100% magnification).

This post (same post linked to above) also discusses how to use deconvolution sharpening in Lightroom, which I can't speak to, because I don't use Lightroom.

Since I've done my deconvolution sharpening examples below using Rawtherapee, here is a link to their little bit of info about it pertaining to Rawtherapee, where there is also a link to the Wikipedia on it: Richardson Lucy (RL) Deconvolution Sharpening. I am also a Gimp user and there is also a deconvolution filter in the G'mic plugin as well*, if you're interested. It's not as robust as the filter in Rawtherapee, but it works. (It doesn't have the 'amount' and 'dampening' options, but it does have two blur type options that I haven't fully explored yet.)

Without further ado, here below are some examples. First, I offer a 100% crop from a K-5, DA15, ISO80, F22, 30 second image. The only adjustment to the DNG in Rawtherapee was to turn on a K-5 dcp, using the embedded tone curve.

The cropped image on the LEFT has the RL deconvolution sharpening turned ON and turned up high (settings also pictured below) and the image on the RIGHT is with deconvolution turned OFF.


Here are the Rawtherapee deconvolution settings for the above example:


Next we have the full sized version that the above crop was cut from, just resized to 1024px wide. I also applied USM after resizing on both images (same amount to both versions).

This is with deconvolution sharpening turned OFF:


This is with deconvolution sharpening turned ON:


Next, the same image worked up rather aggressively into a black and white version using Rawtherapee. The resize, some dust spot healing and same amount of USM was applied to each in Gimp.

This is with deconvolution sharpening turned OFF:


This is with deconvolution sharpening turned ON:


These were the deconvolution settings used for the black and white version:


*Here's the deconvolution sharpening filter available in the G'mic plugin manager for Gimp:


Finally if anybody actually manages to make it to the bottom of this post, here's the full sized unprocessed image in 16-bit tiff export from Rawtherapee hosted at Mediafire, for anybody who might be interested at downloading both versions to compare:
With deconvolution sharpening turned ON (93MB)
With deconvolution sharpening turned OFF (93MB)

So, all that to say, go give it a try! And let me know what you think!

---

Last edited by todd; 04-13-2016 at 06:47 PM.

[The Squirrel Mafia]

It is a very powerful sharpening tool. I use it on occasion in RawTherapee as well. Good stuff!

[Digitalis]

I know this is new and exciting to you, but it is possible to get a superior result through using clever sharpening techniques:


1:1 crop - This was a quick slapdash effort of about 30s using nothing more 2 than high pass filtration masks, channel selective USM & global luminosity USM.

[VoiceOfReason]

I have tried sharpening in post, but always seem to introduce noise.

[Digitalis]

The solution to that is not to use single pass sharpening like most RAW processing suites do,using photoshop allows for tremendous control over how your images are sharpened. Though the trade-off is the time it takes to learn how to treat each image: tbut as you get more proficient, the less time it takes you to get an image to look great.

[Fcsnt54]

Never heard of deconvolution before, thank you for mentioning it. I might need to check it out

[todd]

I know this is new and exciting to you, but it is possible to get a superior result through using clever sharpening techniques:

Your method does look to address the diffraction in a superior way, but the thing I've been liking about deconvolution sharpening is that I can apply it in the raw conversion in Rawtherapee before I go to gimp with my tiff for selective edits and applying additional sharpening methods.. Maybe Lightroom also has high pass options but Rawtherapee doesn't...

So thank you for the food for thought. Going to experiment with high pass again at some point here and compare things... I'll be trying to combine them too and compare those results as well.. It's been years since I tried high pass because I never got anything clearly superior from using it... I know there are some technical reasons behind it's effectiveness at preventing haloing and such. It's possible that the high pass options in gimp and g'mic are not as effective as what's available in Photoshop. And of course I probably wasn't doing it right anyway...

[virusn3t]

Interesting thread (very interesting) suscribed and tomorrow will read more slowly, thanks for the tip.

[HYS]

Nice reading! Thank You!

[Digitalis]

Maybe Lightroom also has high pass options but Rawtherapee doesn't

LR doesn't have it either. And in any case Images that require specialized sharpening techniques should always be worked on in photoshop, with a graphics tablet preferably as they make the process of masking more precise and intuitive.

It's possible that the high pass options in gimp and g'mic are not as effective as what's available in Photoshop.

Third party High pass filtration should be identical to that of Adobe photoshop.

[todd]

Third party High pass filtration should be identical to that of Adobe photoshop.

I was thinking about your result and you are applying more than just high pass versus my original comparison that was just using deconvolution (because I wasn't trying to get the whole sharpening job done in one crack but show what deconvolution can do as an extra step for diffraction).

I ran a quick comparison below. The left is just deconvolution. The right is just a high pass. Deconvolution wins through my spectacles..



Here are the high pass options I selected in g'mic (default).. I don't think anything more would have been an improvement... Once the high pass was applied to my layer I switched to overlay blend as I recall that's the usual method for high pass, right?...

[Digitalis]

I switched to overlay blend as I recall that's the usual method for high pass, right?

Correct, however I used two High pass filters one with a radius of 2.4 and a second with 1.2 both @ 50% contrast. Also I used USM applied with the following settings : Amount =60 Radius =2 Threshold=0 tuned to the orange/red channel and a global Luminosity mask USM @ Amount =120 threshold 0.8 Radius=0 on a luminosity channel.

I have Raw therapee 4.1.22 running on my laptop - I had it because, why not? I can't seem to find the high pass filtration options on the detail tab, where it should be.

Deconvolution wins through my spectacles

But you have a long way to go to match the example that I posed above, and I wasn't just relying on one sharpening method.


FYI you really should clean your camera sensor:

[Nass]

Fyi, if you want to give deconvolution a go but don't have Rawtherapee, there's a freebie I use which does the same - image analyser. It's helped eliminate slow shutter speed unsharpness blur for me before - the original of this had the seal with double whiskers:

[jumbleview]

I knew about Rawtherapee, but never tried it. I should. Thanks, Todd for posting. And thanks to Nass for the reference to MeeSoft
Seems to be be useful stuff there.

[todd]

I wasn't just relying on one sharpening method.

This is where I am not understanding your response completely, because I am purposely just showing one isolated step in a sharpening/editing process, to attempt to show it's effectiveness and counteracting the blur. I can run all kinds of additional sharpening methods to further sharpen the image as you have done... I use wavelet sharpening in Rawtherapee and Gimp a lot which is another effective sharpening tool... I am appreciate of your efforts here so that I can start putting some sharpening methods together to compare with yours but I wasn't trying to show an ultimately sharp 100% crop above.

FYI you really should clean your camera sensor

Yeah this was from a couple years ago or so and it was cleaned shortly after I saw the photos from this session... I like your result!

I have Raw therapee 4.1.22 running on my laptop

If you're running Windows x64 on it, here's the latest compiled build 4.2.915 that I am aware of, though no versions have a high pass filter... Filebin - Tag onvjxqhwi9