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09-09-2012, 03:20 AM   #1
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Linux chromatic aberration correction

Hi,

Can anyone recommend a linux RAW processor that has good handling of chromatic aberration?

I have tried darktable and rawtherapee so far. Darktable's CA seems to be pure autopilot - no control?? RawTherapee's one does something but it's not very usable, having to wait 5-10 seconds to re-demosaic the entire image just to see how the setting looks for your little view area.

I really need what Adobe Camera Raw gives you-- where you can hold down a key and have it only show the relevant colour channels, combined with near-instant responsiveness to changes in the settings, so that you can very easily see the effect of and fine tune the CA correction.

Is this possible in any of the open source linux RAW packages?

(yep - working with crappy lenses.)

09-09-2012, 03:51 AM   #2
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I stopped using Linux at home for just this reason - almost all the top photo software runs on OS X and Windows. So now I have both!

I'm sure this isn't the answer you're looking for, but I really think it's your best answer, even if you have to run one of those under a VM (but that may not allow correct color calibration). I could get just about any other application I needed under Linux, but when it came to photography, it was utterly impractical. This fact was so obvious to me that I didn't even start down that road. I think the clincher for me was the need for mature photo printer drivers - but you lose so much more than that!


I can shoot Pentax, I can run Capture One instead of Adobe products, I refused to buy an iPhone but instead waited for the first ever Android to be released (on the 4th largest network, no less), and a plethora of much more obscure product choices that many people never consider. I do it the hard way, picking the non-mainstream, less supported product for almost everything I buy. But one thing I will not do is try to run photo software on Linux.


OS X is cheap, and Win 8 will be relatively cheap until January!

Last edited by DSims; 09-09-2012 at 04:46 AM.
09-09-2012, 04:04 AM   #3
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QuoteOriginally posted by russell2pi Quote
I really need what Adobe Camera Raw gives you-- where you can hold down a key and have it only show the relevant colour channels, combined with near-instant responsiveness to changes in the settings, so that you can very easily see the effect of and fine tune the CA correction.
This is one of the reasons people pay hundreds of dollars for Photoshop, it makes certain tasks easier. The free software can achieve the same results, but the process will be different and possibly require more work. It isn't enough of a reason for me to spend the money, but that is just my choice.

You could buy better glass for the cost of Photoshop.
09-09-2012, 04:45 AM   #4
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Yeah - I have Adobe CS on my work laptop... but with my other laptop I am trying to stick to free software in Stallman's sense (as in 'free speech', not 'free beer'). I can resort to unfree s/w if needs be but am curious as to what's available. It ought not to be that hard. If I had time I'd fix it myself.

09-09-2012, 06:30 AM - 1 Like   #5
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Did you have a look at various GIMP plugins? like Purple Fringe or fix-ca. I have them both installed on GIMP 2.8 but i have no clue whether they satisfy your expectations. Just try them out.
09-10-2012, 03:18 AM   #6
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Problem solved - darktable actually works out the correction from the lens type and settings and was doing a pretty good job.

I just couldn't tell because the override sliders did nothing. Once I told it the correct lens model (all s/w, Adobe included, seem to get this lens wrong) the auto correction got even better and the override sliders also worked.

Very good -- better than Adobe Camera Raw in this respect at least!
09-10-2012, 03:31 AM   #7
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Most Linux converters can make use of the Lensfun library. Lensfun is designed to correct distortion, transversal (also known as lateral) chromatic aberrations, vignetting and colour contribution of the lens (e.g. when sometimes people says one lens gives "yellowish" images and another, say, "bluish").

I did find that my UFRaw version wrongly (or not at all) identified the Sigma 17-70mm (old version) which meant I had to manually pick it from the dropdown. I've gotten a bit more adventurous since and patched exiv2 which is where the problem originated. Of course, mis-identification with Sigma lenses is not limited to Linux alone - Sigma seems to have used different codes in its in-lens chips leading even to miscommunication with some Pentax bodies. My old 24-135mm used to cause the LCD on my K100D-Super to black out until I had it rechipped.

Back to lensfun: I find it is always best to grab the profile-database directly from the SVN development server. It is an XML file that's easily integrated into an existing system (lives somewhere in /usr/share/lensfun). The URL is WebSVN - lensfun - Rev 175 - /trunk/data/db/
09-10-2012, 03:37 AM   #8
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Examples of calibration data for distortion, CA and vignetting are below. Please note that all lenses have distortion data but certainly not all heve CA or vignetting data in LensFun so YMMV:

QuoteQuote:
<lens>
<maker>Pentax</maker>
<model>SMC PENTAX DA 40mm F/2.8 Limited</model>
<mount>Pentax KAF2</mount>
<cropfactor>1.5</cropfactor>
<calibration>
<distortion model="poly3" focal="40" k1="-0.00384" />
<tca model="poly3" focal="40" br="-0.0000230" vr="1.0001421" bb="0.0000150" vb="0.9999150" />
<vignetting model="pa" focal="40" aperture="11" distance="1000" k1="-0.17248" k2="0.21247" k3="-0.13119" />
</calibration>
</lens>
QuoteQuote:
<lens>
<maker>Pentax</maker>
<model>SMC Pentax DA L 18-55mm f/3.5-5.6</model>
<mount>Pentax KAF2</mount>
<cropfactor>1.5</cropfactor>
<calibration>
<distortion model="ptlens" focal="18" a="0.00117" b="-0.01707" c="-0.00529" />
<distortion model="ptlens" focal="24" a="0" b="-0.0071" c="0" />
<distortion model="ptlens" focal="35" a="0" b="0.0002" c="0" />
<distortion model="ptlens" focal="42.5" a="0.00291" b="-0.00765" c="0.00808" />
<distortion model="ptlens" focal="55" a="0" b="0.00333" c="0" />
<vignetting model="pa" focal="18" aperture="11" distance="1000" k1="-0.26538" k2="0.5437" k3="-0.51036" />
<vignetting model="pa" focal="24" aperture="11" distance="1000" k1="-0.08271" k2="0.02282" k3="-0.04481" />
<vignetting model="pa" focal="35" aperture="11" distance="1000" k1="-0.05666" k2="0.02789" k3="-0.01283" />
<vignetting model="pa" focal="42.5" aperture="11" distance="1000" k1="-0.03675" k2="0.01041" k3="-0.00479" />
<vignetting model="pa" focal="55" aperture="11" distance="1000" k1="-0.07077" k2="0.07738" k3="-0.04494" />
<tca model="poly3" focal="18" br="0.0000246" vr="1.0008065" bb="0.00025" vb="0.9998" />
<tca model="poly3" focal="24" br="0.00004" vr="1.00056" bb="0.00024" vb="0.9999" />
<tca model="poly3" focal="35" br="0.00001" vr="1.000127" bb="0.000022" vb="1.0001" />
<tca model="poly3" focal="42.5" br="0.000084" vr="1.0000218" bb="-0.0000375" vb="1.0000794" />
<tca model="poly3" focal="55" br="0.0000165" vr="0.99999" bb="-0.0000538" vb="1.0000742" />
</calibration>
</lens>


09-10-2012, 05:45 AM   #9
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Very cool.
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