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How to fix CA in Aperture 3?

S

sebascrub

macrumors member
Original poster
Jun 2, 2007
96
0
Calgary, AB
I took this photo of my cat the other day and I really like it, save for the purple on her whiskers. This is what they call chromatic aberration, right? Is there any way to fix it in Aperture 3? I've been playing around with it for a bit, but can't seem to find the right workflow. The biggest problem seems to be that the whiskers are so thin and I can't really apply brushes to them effectively. I'm pretty new to Aperture, so I'm probably missing something really obvious. :eek:


DSC_0243 by sebascrub, on Flickr
 
There is an option to remove chromatic aberration in Aperture, you need to find it in the list with all the other adjustments you can make. You'll have to fiddle around with the various settings but you should be able to remove the colour.
 
Aperture only removes red/cyan and blue/yellow chromatic aberation. Your picture appears to have purple/green chromatic aberration which is either lateral chromatic aberration or spherical aberration (see "The Seven Deadly Aberrations" for more info). Your best bet there is to convert the image to black and white, and optionally apply a tint to it. If you find that many of your images have this aberration, you will want to consider a different lens.

If you do want to try the chromatic aberration cleanup settings in Aperture, start by double-clicking on the photo, go to the Adjustments tab in the upper left, and then click on the "Adjustments" drop down right under the histogram. From there, select "Chromatic Aberration" and you will now find adjustment sliders below to correct CA.

I have found that the CA correction in Aperture is fairly lacking compared to DxO Optics Pro. DxO uses detailed profiles for each camera and lens combination to obtain the best possible CA removal results. There is a demo version available so that you can see how it compares. That said, it might be better to put money towards a lens with improved optics rather than spending the money on DxO.

Good luck and hope this info helps!
 
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The "halo reducer" brush is what you want to use to get rid of the purple. It's been a while since I've used Aperture but take a look at it. What you're seeing there is often referred to as purple fringing, not chromatic aberration.
 
chrfr said:
What you're seeing there is often referred to as purple fringing, not chromatic aberration.
Click to expand...

Actually, purple fringing is a form of chromatic aberration... it is lateral chromatic aberration. This guide explains the various forms of CA in more detail.
 
Ah! I didn't even see the Chromatic Aberration option under Adjustments. I tried playing with the sliders, but jabbott is right: it can't really remove the purple aberration. I then tried the Halo Reduction brush, but it didn't make much of a choice. The best solution was indeed to convert it to black and white, which didn't really affect the photo too much since she's already pretty black.

I shot this with my 35mm f/1.8 and I've never really encountered too much CA in my previous photos. The only other time I've seen it is when I have light glinting off metal, like if I'm shooting my guitar's tuning pegs or something. Luckily, I mostly do concert and street photography and it hasn't been too big a problem.

Thanks so much guys (gals?) for your enormous help! :D
 
If you have photoshop you can paint that out pretty easily with the desaturate brush (keep it at like 90% so you still have a little color and be careful to stay roughly within the lines), since the subject and surroundings are mostly pretty neutral.

Virtually all lenses have this problem, and only two really solve it from what I understand: the $6000 coastal optics 60mm f4 macro and the $1500 (used, discontinued) 125mm f2.5 apo-lanthar. There are others, too, I think, but not many.
 
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Policar said:
If you have photoshop you can paint that out pretty easily with the desaturate brush (keep it at like 90% so you still have a little color and be careful to stay roughly within the lines), since the subject and surroundings are mostly pretty neutral.

Virtually all lenses have this problem, and only two really solve it from what I understand: the $6000 coastal optics 60mm f4 macro and the $1500 (used, discontinued) 125mm f2.5 apo-lanthar. There are others, too, I think, but not many.
Click to expand...

Unfortunately, I don't have Photoshop... far too poor for that!
 
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