06-14-2011, 10:11 PM
That looks like longitudinal CA to me.
There are two types of CA, lateral and longitudinal.
Lateral CA is caused by different magnification of different colours. It gets worse as you go away from the centre of the image. That is the "easy" one to correct as it is a matter of applying different magnification to the colour channels of the image.
Longitudinal CA is caused by the focus planes of each colour being at a different distance and not a single plane. This commonly results in purple and blue-green fringing which can happen anywhere in frame, depending on if it is in front or behind the focal plane. This is the hard one to process out. It does reduce in strength as the aperture is closed. You might be able to get away with a global selective colour desaturation as a quick fix, assuming there are no other strong "purple" areas in the image.
There are two types of CA, lateral and longitudinal.
Lateral CA is caused by different magnification of different colours. It gets worse as you go away from the centre of the image. That is the "easy" one to correct as it is a matter of applying different magnification to the colour channels of the image.
Longitudinal CA is caused by the focus planes of each colour being at a different distance and not a single plane. This commonly results in purple and blue-green fringing which can happen anywhere in frame, depending on if it is in front or behind the focal plane. This is the hard one to process out. It does reduce in strength as the aperture is closed. You might be able to get away with a global selective colour desaturation as a quick fix, assuming there are no other strong "purple" areas in the image.
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