Image quality

Color fringing

Written by Bernard Dery

Chromatic aberration and purple fringing are two distortion effects that can negatively affect photographs. There are a couple of things you can do to minimize these effects.

Color fringingChromatic aberration and purple fringing are two distortion effects that can affect photographs. Even though they are often confused with one another, they are partially different in both their causes and effects.

Chromatic aberration can be seen in photos as light colored purple halo around parts of a scene. Manufacturers try to correct it by designing specialized lens elements and coatings.

Since no lens is perfect, especially zoom lenses, chromatic aberration is likely to remain visible at some focal lengths and apertures. Superzoom lenses are often more prone to chromatic aberration at their extreme focal lengths because zoom lenses are optimized at intermediate focal lengths.

Purple fringing is caused primarily by the processing done to every image by digital camera processors. The processor doesn’t always know how to interpret dramatic color. Purple fringing is, yes, primarily purple but it can be magenta and other colors as well.

Avoiding chromatic aberration and purple fringing

Both effects are in a good part lens-dependent and thus cannot be completely avoided. However, these effects will be lessened by carefully exposing scenes with very high contrast, such as tree branches against the sky. Using a lens at its middle rather than extreme focal lengths will help avoid chromatic aberration or purple fringing.

Some photo editing software have tools to remove or reduce the effects of fringing.

About the author

Bernard Dery

Bernard was born and still lives in Quebec City, Canada. A doctorate candidate in Physics, Bernard works full-time as an optical designer at EXFO, a world leader in telecom tests and measurements tools. His professional interests go from fiber optics to atmospheric data collection and lasers.

His first contact with photography was a Vivitar fixed lens camera that he had purchased at age eight. His interest developed slowly, and for many years Bernard limited himself to family and travel pictures.

Bernard discovered the world of digital photography in February 2004, when he purchased his first digital camera. Developing an interest for composition, he experimented with many subjects: landscapes, nature, cities and architecture.

Bernard
soon began to invest more time and energy into his new found hobby, finding new and beautiful subjects to capture everyday. His challenge is to capture the mood and emotion carried by a scene as it presents itself to him.

A trip to Italy in
September 2004 fueled his growing interest with numerous magical photography opportunities.

Bernard and his wife like to spend free time near a lake at his family's summer house, where he finds new subjects to capture every day. His interests are varied and include hiking, camping, swimming, boating and reading, as well as most winter
sports.

Bernard, known as bdery on forums, uses a Pentax K20D and W80, Canon S2 and a Nikon SQ as a backup.

Thumbnails are of photos by Bernard Dery - used with permission
Copyright Bernard Dery All rights reserved