Camera Technician Question:

Also known as color fringing, chromatic aberration occurs when the collective color wavelengths of an image fail to focus on a common plane. The results of chromatic aberration are most noticeable around the edges of high-contrast images, especially toward the edges of the frame. Chromatic aberration is most common on less expensive lenses, although even the best optics can occasionally display lower levels of chromatic aberration, under certain conditions.