[Brightcolours]

[quote name='genotypewriter' timestamp='1291435398' post='4752']

I can't see how this can be true for phase detect AF. Also if you're focusing on something black and white, the human eye can't differentiate between red, green and blue. But you still get fringing.



It's true that a Bayer sensor sees more contrast in green but I doubt it's the cause for PF because, like I said, PF doesn't exist with well corrected lenses.



So far the most suspicious thing to me is LoCA reacting with surrounding photosites.



GTW

[/quote]

If different colours have different focus planes, it may well be that AF systems are made to be more receptive to green in order to get the best results for us, the viewers of the results. Of course, black and white are not colours of light, so the same applies.



PF and LoCA are NOT the same thing. LoCA is green and magenta.

PF is purple to blue-ish (usually, it can also appear towards red oddly enough).

Nice PF example from the Sony 16mm f2.8 fisheye:



PF in lovely "orbs":



PF like we know it from compact digitals:





Longitudinal Chromatic Aberration:



LoCA from Canon EF 100mm f2.8mm macro:





Photosites do not "react" to eachother, LoCA is lens dependent. PF is lens dependent too, and seen mostly with cheaper compact digital cameras. Manufacturers have made changes in back element coating to combat PF, Sigma has introduced the DG(DC) line and Tazmron the Di(Di II) line specifically for PF (not LoCa). Nowadays you do not see PF very often anymore. You do see a lot of LoCA still, specifically with wide aperture lenses and macro lenses.

LaCA ("normal" CA) is mostly seen with standard zooms and wide lenses, but also with other lenses. Some brands show laCA more (often) than others (Nikon, Tokina, Pentax come to mind).