Old 09-02-2007, 12:55 AM   #1
Flowing
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Default Purple Fringing

My new toy (Nikon D40) is a great little camera but I've noticed a fair amount of purple fringing along thin lines that contrast heavily with the backround (especially tree branches and leaves). I am using the kit 18-55 lens (which received great reviews). Is purple fringing more of a product of the image sensor or the lens?
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Old 09-02-2007, 02:18 AM   #2
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Quote:
Originally Posted by Flowing
Is purple fringing more of a product of the image sensor or the lens?
It's primarily a result of the lens and is most likely to be seen in areas of high contrast. The design of the lens plays a big part in how well purple fringing is controlled check out the following links for a more detailed answer.

http://www.dpreview.com/learn/?/key=...tic+aberration

http://en.wikipedia.org/wiki/Purple_fringing
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Old 09-02-2007, 04:54 AM   #3
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The purple fringing you're referring to is called Chromatic Abherration. It is very hard (re: expensive) to eliminate but it can be done by using either an Ultra-Low Dispersion element or Apochromatic elements (Canon L = Ultra Low Dispersion, Sigma APO = Apochromatic). Basically, the glass in the lens refracts differing wavelengths of light at different angles. The thicker the glass, the bigger the angle difference, and the Ultra-Low Dispersion element corrects for this by being extremely thin. Apochromatic elements have a special coating on the inside of the elements that also is very effective in reducing abherrations.
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Old 09-02-2007, 05:11 AM   #4
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In Photoshop (maybe even elements), go to Image>Adjustments>Selective Color, Scroll Down to Magentas and set the Black and Magenta sliders to 0 and mess around with the rest until you get a good result. Works 85% of the time.
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Old 09-02-2007, 10:59 AM   #5
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I've never gotten around to trying PTLens but have seen mention of its effectiveness on various boards.

http://www.epaperpress.com/ptlens/
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Old 09-03-2007, 08:56 AM   #6
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Quote:
Originally Posted by JRMDC
I've never gotten around to trying PTLens but have seen mention of its effectiveness on various boards.

http://www.epaperpress.com/ptlens/

The results certainly look impressive
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