Chromatic aberration (CA) is the green and purple fringe (or halo) that appears around contrasting objects - usually near the edges of a picture. Thirty years ago, when everyone used fixed focal length prime lens, chromatic aberration was evil. It appeared only in inferior lenses.
In the digital era, where zoom lens rule, chromatic aberration is relatively common. The image below is a good example of chromatic aberration gone bad. It was taken with a $1000.00 Nikon 12-24mm DX zoom lens. Yech!
"CA be fixed with software"
Experts say: "CA is not a problem anymore. It can be fixed with software."
Yes, but only if the CA is 1 or 2 pixels wide in a 100% enlargement. If the CA is as bad as that produced with the 12-24mm DX zoom lens, you are out of luck. In this image, some of the CA was 8 pixels wide. Software will either miss it, distort it or remove other details.
Look at the image below. It shows how software can fail to fix really bad cases of CA.
Note how the image has become deformed and distorted by the software's failed attempt to remove CA.
Sorry folks, but nothing has changed in 30 years. CA is the sign of an inferior lens. The best lenses don't have CA. Don't let anyone convince you otherwise!CA that is more than 2 pixels wide just sucks.
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