Purple fringing is another common problem that you will encounter in digital photography. It's caused by the optical design of a lens, and is different from the standard chromatic aberration. Purple fringing is typically found around bright highlights, and can usually be seen around shiny points on metal. It's also common on water highlights, and it is usually worse on less expensive or poorer quality lenses. It still does present itself on expensive and high-end glass, however. Aperture does have a tool for fixing this problem called the Halo Reduction brush, but it's not very good. There is, however, another relatively simple way to fix purple fringing using some of the other tools in Aperture. The following steps explain what to do:
With an image that is experiencing the color fringing problem, the first thing to do is zoom in to 1:1 so you can get a better look at what's happening. You may need to make some fine adjustments, so zooming in is essential to see the...