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| p.1 #10 · when sagittal and tangential Spatial frequency curves don't coincide |
S Dilworth wrote:
Well, no, because it's defined at the focal plane. A lens with longitudinal chromatic aberration would produce false colour just outside the focal plane, but so might a lens with very little longitudinal chromatic aberration, for other reasons (such as spherochromatism). This is why modern lenses, despite having less longitudinal chromatic aberration than older lenses, often have more saturated false colour just outside the focal plane.
Even some apochromatic lenses (with three colours brought into focus and very minimal tertiary colour) have lots of false colour just outside the focal plane.
isn't spherochromatism not at all uniform across the image though? And I believe you can see LoCa spread well into OOF areas at times. Take a 300 f/4 non-IS L and shoot into some pine woods at f/4, you see a green clouding around needlesbranches farther back and purplish in front (uniformly across the frame, same degree in center as mid point as at edges and not swapping of which color is smeared front vs back)