Taking some test shots with a Nikon D2X and Nikkor 28mm 1.4,I stumbled onto an interesting color fringing result that I'd like help understanding. Chromatic aberration occurs for the following reason according to the explanation found at http://www.paintedstork.com/digiblog/2005/07/correcting-chromatic-abberations.html:
Why does it happen?
This happens due to an optical phenomenon called chromatic aberration. Refractive index of a glass is sensitive to wavelength of the light. This means that all colors do not focus on the same plane. Violets and Reds, which are on the edge of visible spectrum would get focused at different plane than others and hence create these colored edges.
Here are some good links on CA:
- Good Nikonian Thread How to Test Lens for CA?
- Interesting CA summary from Van Walree's web site referenced by above thread: Chromatic Aberrations
Here's the situation I ran into:
Taking some test shots of a coffee cup and lens cap I was surprised to find two identical exposures having different color fringing. I'm assuming this happened because the camera was hand held and the angle of the shot changed slightly each time.
I took 3 photos (seen below). The first had the most fringing at F/1.4. The second and third taken at F/2.0 had less, but one had green fringing and the other blue.
I'd like to understand why this difference in fringe color occured on the 2nd and 3rd shots. My test shots were spontaneous and hand held, and I'm guessing that the position and angle of the lense relative to the subject and or change in focus is the cause of the color change in the fringing. The photo with green fringe (2nd below) was manually focused and not as sharp as the autofocused version with blue fringe (3rd below). Insights appreciated.
The lighting for all 3 photos was the same, desk Ott-Lite and an open window. All three photos were taken within about a 10 min span.
Thanks for your help.
August 10, 2006 Update: This question was posted at Nikonians.com on this thread. Got some good feedback there (thanks Nikonians!), one post referenced this interesting link: The Dreded Purple Fringe.
* Note: Thumbnails are 10% of original and blowups 180% of original.
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