Originally Posted by Alex Leith
Chromatic abberation.... a side-effect of the fact that different wavelengths (colors) of light resolve at different points (because they bend different amounts) when they pass through a lens. It results in a red-blue or magenta-green fringe most visible on high-contrast edges, especially at the edges of the image.
Zoom lenses suffer more than primes as zoom lenses pass the light through more lens elements.
Very succinctly stated, Alex. Great post! I would only add that CA is harder to tame as the resolving power of a lens gets higher. Like other fine details in HD, CA gets more noticeable as well.