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Old Jan 26, 2011, 8:14 AM   #1
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Default Free CA Removal Tool

I used to use Photoshop Elements 7 (PSE7) but switched to Photoshop CS3 because PSE7 didn't have an automatic tool for removing "purple-fringing" or "chromatic aberration" (CA). While CS3 has CA compensation sliders in its Adobe Camera Raw (ACR) program.

This means, however, that I have to shoot in RAW to use ACR. Although Photoshop CS3 has CA sliders under its "lens distortion" filter, they do not do as good a job as ACR's in my experience.

I found out that Photobee.exe which comes with Dynamic Photo HDR has an excellent CA removal tool. It works just as well if not better than ACR's. It can work with both some RAW formats and JPEG.

#1) With CA


#2) No CA.


#3) CA close-up.


#4) No CA close-up.


#5) With CA


#6) No CA.


Photobee's CA removal tool: You drag ball on the left up and down to control red/cyan fringing and left and right to control blue/yellow fringing.


You can download Photobee.exe by downloading a trial version of DPHDR. AFAIK, you don't have to purchase DPHDR. (But you could -- only $55 -- it's my HDR program of choice.) Installing does not create a shortcut for Photobee.exe but you can find it in the same directory where DPHDR is installed. Photobee also comes with many powerful editing features similar to Photoshop's.

I just thought I'd share this as I've been looking for a free or inexpensive CA removal tool and couldn't find any. For me, if cleaning up fringing is the only reason for moving up from PSE to CS, then it doesn't justify the high difference in cost.

Last edited by vvcarpio; Jan 26, 2011 at 8:28 AM.
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Old Jan 26, 2011, 8:49 AM   #2
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I just want to mention that there are two kinds of CA -- "lateral" and "axial" (sometimes called "longitudinal.") It looks like this tool is going after lateral CA, which is often removed automatically in the camera any more if you shoot JPEG. For raw data, the camera's RAW converter may automatically remove it (Capture NX2 can do this for Nikon shooters.)

Lateral CA seems to be the kind of CA that lens makers opt for when designing lenses nowadays, presumably because it is so easy to remove in pp. For example, both the Nikon 35mm f/1.8 and the Tokina 12-24mm f/4 lenses have heavy doses of lateral CA that, if you use the auto CA suppression, you will never see.

However, the tough CA to remove is the axial CA. This is still present in some lenses to some degree. My Tamron 90mm f/2.8 suffers from axial CA under difficult shooting conditions (e.g., black tree branches back-lit against a bright sky.) AFAIK, there is no auto removal of axial CA. Capture NX2 has a slider to allow you to manually adjust until it is minimized, but this seems to always be a human intervention with current technology.

The difference between these two kinds of CA, btw, is that axial CA is caused by different frequencies of light focusing at different focal depths, while lateral CA is due to misalignment laterally (of course) on the focal plane of different light frequencies. So axial CA will always lower the sharpness of the image when present, even if you suppress its appearance. When lateral CA is removed, the optimal focus of the image is restored, so it is benign enough that lens manufacturers seem pretty indifferent to its existence. People who have older-generation cameras may still see this effect. It is not uncommon for people with a D40 to complain about the poor quality of the 35mm lens, while folks with more recent cameras have no idea what they are complaining about. FWIW
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Old Jan 26, 2011, 12:20 PM   #3
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I didn't expect to get so much info when I posted this. Many thanks, tclune!
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