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Fringing + Canon L lenses

Asher Kelman

OPF Owner/Editor-in-Chief
Axial CA, as it is distributed on progressively further focal planes, must get larger. Horizontal CA then, from optics misfocus, then is magnified for reason inherent in the lens design or else flaws in the glass or centering?? Ill read Bart's link for the latest Adobe Raw engine solutions.

Thanks, Bart, Doug and Jerome for you knowledgable insight. It makes me feel fortunate already to have a lens with such decorative renderings!

asher
 

Doug Kerr

Well-known member
Hi, Asher,

Horizontal CA then, from optics misfocus, then is magnified for reason inherent in the lens design or else flaws in the glass or centering??
Not sure I know what you mean. Lateral CA comes basically from the fact that the glass used in lenses has a differing index of refraction over different wavelengths in the visible spectrum. Thus the refraction of light as it passes across each lens surface lens will be different for different wavelengths.

Lens designs attempt to compensate for this by making the phenomenon in different elements have opposite sense at the focal plane, thus cancelling out the undesired result. But of course that can't be done completely (not and do all the other things a lens design is asked to do)

Thus the cones of light of different wavelength from the same point on the scene, even if they all come to a focus on the focal plane (assuming that the lens is focused, and absent any axial CA), may do so at different places on the focal plane (different distances from the center).

Best regards,

Doug
 
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