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Images from the new 75mm f1.8, some aberration

Discussion in 'Olympus Cameras' started by RichA, May 25, 2012.

  1. RichA

    RichA Mu-43 Regular

    120
    Mar 28, 2012
    Spherical aberration occurs when light rays going through near the edge of the lens come to a shorter focus point than those going through the centre.
    This could be a manifestation of the closeness with which the lens was used for the close-up flower shot. If you look at the other images, you don't see it.
    Spherical aberration here manifests as a thin, defocused halo around the objects. Look at the yellow parts of the flower image. It's also possible it is sphero-chromatism a combination of spherical and chromatic aberration. To test for that with a lens, you look at objects beyond focus and inside focus. If there are two colours in the defocused parts, like the halo is green on one side and purplish on the other, it's spherochromatism.

    Although the fast 75mm uses ED and HR type glass to control chromatic aberration, it doesn't say if it uses any aspheric surfaces which control spherical aberration in fast lenses. The Nikon and Samyang 85mm lenses both use molded (glass or plastic) or hybrid (laminated plastic on glass) lenses to control spherical aberration.

    Also, spherical aberration in a soft form can look like a general lack of contrast in an image as well because peripheral light rays are out of focus and diffused across the image. This is more apparent in close-focus situations since most (other than macro lenses) lenses are designed to operate best at infinity.

    M.ZUIKO DIGITAL ED 75mm f1.8 | OLYMPUS E-SYSTEM | Olympus Imaging Asia