05 Chromatic Aberration option
If you don’t see the Chromatic Aberration tool in the adjustment panel, you’ll need to open it via the Add Adjustment menu at the top. Aperture only displays a selection of its adjustment tools here, but you can choose which ones are displayed by default – see Step 10.
06 Suck it and see
This tool has two sliders – one for correcting Red/Cyan fringes and one for Blue/Yellow. Remember, chromatic aberration appears as complementary colour pairs – these are the two most common.
You need to take a look at your image and work out which colour pairing is the closest. Here, I think I need to adjust the Red/Cyan slider.
From now, it’s just a case of moving the slider one way and then another to see the effect it has on the colour fringing. Sometimes you need to push the slider too far and ‘overshoot’, then work back to get a feel for the best position.
Here, a value of -0.45 looks like it’s giving me the best result.
07 Secondary adjustments
I’m not sure I’ve got rid of all the fringing, though, or that what’s left is still this red/cyan colour. This is quite common. Many lenses actually produce magenta/green fringes, and Aperture doesn’t have a slider for this one. But you can still correct these fringes by using the Red/Cyan and Blue/Yellow sliders together. This does, in essence, produce a magenta/green correction.
This is borne out by my image. After the red/cyan correction, what’s left does look blue/yellow in colour, and a slight positive adjustment to the Blue Yellow slider (+0.27) gives me a result that’s as close to neutral as it’s likely to get.