85mm 1.8 Purple Fringing at f1.8

Started Jul 6, 2010 | Discussions thread
bronxbombers
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Re: CA and CA
In reply to gdanmitchell, Jul 9, 2010

gdanmitchell wrote:

Jan Madsen wrote:

Both the abberations you describe are chromatic abberation. The first is lateral CA, easy to correct in PP, zero at center and worst in the corners. The second is longitudinal CA, seens as purple, green or red halos around edges all over the image - more difficult to remove.

In the broadest sense of the term, perhaps. But in photography when people refer to "CA" (or chromatic aberration) they are referring the thing that is correctable using the red/green and yellow/blue sliders in post-processing software and which appears purely as a result of lens capability... in virtually all lenses. (Your description is odd - this manifests as the mostly red and green "halos" you describe and IS easily correctable in post.)

When they refer to the "purple fringing" effect caused by sharp borders between blown out and dark areas they are recognizing a different thing with a different cause and a thing that cannot be fixed in the same way.

It is not helpful to suggest that they are the same thing - they are most certainly not and you must deal with them in completely different ways.

Dan

but longitudinal CA is longitudinal CA and if it is CA it is CA

and is it helpful to make it seem like some mysterious thing created by the sensor?

stopping down (not that you may want to) is one way to fix it before it even happens

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