06-15-2011, 07:19 PM
(This post was last modified: 06-15-2011, 07:20 PM by Brightcolours.)
[quote name='wim' timestamp='1308161822' post='9263']
3) Latitudinal Chromatic Aberrations (blue and yellow most often), which also occur in hard contrast transitions, essentially the blue parts in nose and the upper part of the instrument. Some PF is mixed in here as well. LCAs normally occur in in-focus areas. These can also be corrected to a large degree - most software can handle this automatically these days, although this is a rather severe case of these aberrations (plus some PF mixed in). There is quite a large transitional zone here with PF too.
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Wim, La CA usually is green and magenta, or red and green-blue, the yellow and blue variation is relatively rare. LaCA affects the whole image, except the center of the image. The further you go to the edge, the stronger the LaCA will get. It messes up the image's contrast and sharpness, and in contrasty transitions you will see on one side of a darker subject magenta, on the other side green. Or, yellow and blue. Or red and blue-green. The colour depends on which part of the spectrum gets "bent" more or less than the rest of the spectrum, so which colour image has a larger or smaller projection than the rest of the spectrum. If red is the offending part of the spectrum, you will see red and blue-green edges. If blue is the "problematic" part, you will see blue and yellow, And if green is the offending colour, you will see magenta and green.
CA, usually, is correctable, if the optics show a nice and gradual CA shift. It also depends on the "purity" of the offending part of the spectrum, because the software I know only corrects for the different colour channels (R, G or B ). The correcting works by making the image or either the red, blue or green channel larger or smaller, till the size corresponds to the other 2 channels.
There is also software that does not correct, but rather masks, CA by desaturating just the coloured edges. Most in-camera "CA-correction" works that way. This is a less desirable method.
3) Latitudinal Chromatic Aberrations (blue and yellow most often), which also occur in hard contrast transitions, essentially the blue parts in nose and the upper part of the instrument. Some PF is mixed in here as well. LCAs normally occur in in-focus areas. These can also be corrected to a large degree - most software can handle this automatically these days, although this is a rather severe case of these aberrations (plus some PF mixed in). There is quite a large transitional zone here with PF too.
[/quote]
Wim, La CA usually is green and magenta, or red and green-blue, the yellow and blue variation is relatively rare. LaCA affects the whole image, except the center of the image. The further you go to the edge, the stronger the LaCA will get. It messes up the image's contrast and sharpness, and in contrasty transitions you will see on one side of a darker subject magenta, on the other side green. Or, yellow and blue. Or red and blue-green. The colour depends on which part of the spectrum gets "bent" more or less than the rest of the spectrum, so which colour image has a larger or smaller projection than the rest of the spectrum. If red is the offending part of the spectrum, you will see red and blue-green edges. If blue is the "problematic" part, you will see blue and yellow, And if green is the offending colour, you will see magenta and green.
CA, usually, is correctable, if the optics show a nice and gradual CA shift. It also depends on the "purity" of the offending part of the spectrum, because the software I know only corrects for the different colour channels (R, G or B ). The correcting works by making the image or either the red, blue or green channel larger or smaller, till the size corresponds to the other 2 channels.
There is also software that does not correct, but rather masks, CA by desaturating just the coloured edges. Most in-camera "CA-correction" works that way. This is a less desirable method.