Fixing Chromatic Aberrations (That Colored Edge Fringe)
Chromatic aberration is a fancy name for that thin line of colored fringe that sometimes appears around the edges of objects in photos. Sometimes the fringe is red, sometimes green, sometimes purple, blue, etc., but all the time it’s bad, so we might as well get rid of it. Luckily, Camera Raw has a built-in fix that does a pretty good job.
Open a photo that has signs of chromatic aberrations. If they’re going to appear, they’re usually right along an edge in the image that has lots of contrast (like along the edges of this structure).
Press Z to get the Zoom tool and zoom in on an area where you think (or see) the fringe might be fairly obvious (here, I’ve zoomed in on the top right, and you can see thin red and green lines along the edges). To remove this, start by clicking on the Lens Corrections icon (the sixth icon from the left) at the top of the Panel area, then click on the Profile tab to get to the first chromatic aberration control.
In most cases, all you’ll have to do is turn on the Remove Chromatic Aberration checkbox (as shown here) and you’re done—Camera Raw removes the color fringe based on your lens’ make and model, which it learns from the metadata embedded into the image at the moment you took the shot. However, if for some reason the image still needs more correction (the checkbox alone didn’t do the trick, like with this image), then you can try getting rid of the fringe manually by clicking on the Manual tab and using the sliders in the Defringe section (seen in the next step. Just so you can see how this works, go ahead and turn off the Remove Chromatic Aberration checkbox).
We’ll start by trying to remove the red line by dragging the Purple Amount slider to the right, and then also dragging the Purple Hue slider to the right until you see it’s gone. In this case, it removed it nicely. You can do the same thing for the green aberration—drag the Green Amount slider to the right first, and if anything is left over, drag the Green Hue slider to dial in just the right hue, until it’s completely gone. Again, I rarely have to go beyond turning on the Remove Chromatic Aberration checkbox, but at least now if it doesn’t do the job for you, you’ll know what to do instead.