Chromatic aberration sounds technical and beyond the grasp of most of us, but it’s simply color fringing that some lenses create in our photos:
It can be easily fixed by checking the “Remove Chromatic Aberration” checkbox in the Lens Corrections panel.
Watch this short video for more about chromatic aberration, how to fix it, and how it differs from green and purple fringing.
(For best quality, hit Play, then click on the Youtube sprocket wheel 
in the bottom right and choose 720/HD).
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Related Post:
What’s New in Lightroom 4.1: Starting at 0:45, the video below shows how to remove green and purple fringing using controls that were added in Lightroom 4.1
Best vid on the explanation and ways to resolve chromatic aberration. Thanks Laura.
Thanks! Just saved me a TON of cloning work. Loved the information!