Originally posted by jaieger Hey, just wondering - how do I correct CAs of various types (PF mostly, though) in CS5? I try moving around the dials in various combinations but it either exacerbates the problem, or turns the PF into green fringing or cyan. At best, it reduces it a bit. How do I make it take out the CA altogether?
There are a great variety of PF and CA types that can appear in images and it's important to know that some of these simply can't be corrected. The easiest being lateral CA which can almost always be controlled via the lens correction module in RAW of Photoshop. However... in many cases CA or PF can be so problematic that eliminating it becomes impossible. One such case is where CA manifests itself through missregistration within the RGB channels. Which can be visualized this looking at each channel on Photoshop(for example) and identifying the differences between them or... in cases where you suppress one color fringe only to find another and another bellow it(arg).
Anyways, perhaps one of the simplest and quickest ways to manage PF or CA in an image is with Photoshop with this handy little technique shown on
http://www.tgraphic.com Go Filter > Distort > Lens Correction. This will open op a new window with several tools at your disposal. Elements does have a version of this but it doesn’t contain the CA correction sliders.
Just move these sliders till the CA disappears. On images that suffer a lot of CA and PF this may not work so well. If thats the case you will need to take the longer route.
Fixing CA and PF in both CS and Elements
The image below has suffered quite badly from both CA and PF.
Zoom into the bottom right too clearly see these 2 effects.
To remove these you can use a few Hue / Saturation adjustment layers. Add one to your layers window above the main image.
From the drop down menu select Cyans. Now adjust the Hue, Saturation and Lightness sliders till the cyan CA blends in to the rest of the image. Dont worry too much about the colour changes to the rest of the photo for the moment.
Now change the drop down menu to Blues and repeat the process.
Re-name the adjustment layer Cyans and Blues.
Create another Hue / Saturation adjustment layer. Re-name it Reds. Find an area of your image effected by red / purple fringing. Repeat what you did with the last adjustment layer but this time on the Reds and then Magenta channels.
Before
After
When you are happy with the result create a third Hue / Saturation adjustment layer and call it Greens. Find an area that has bright green lines and do as before but on the Green channel.
Before
After
With all the CA and PF taken care of you now need to use the masks so that it only affects the parts of the image where needed. Invert all your adjustment layers mask so they are black. To do this, hold down alt then click the mask. The screen will go white. Press Ctrl I and they will go black. Repeat this for all 3 adjustment layers masks
Starting with the blue and cyan correction layer use the masks to reveal the corrections you made over the CA and PF on the image. Then repeat this for the other 2 adjustment layers. The final result should look a lot nicer. You can even go back to each adjustment layer and tweak them further if needed.