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Sagittal Coma Flare
See also the sagittal flare images for the 18/3.5 Distagon.
Point source rendition (the point spread function) shows various aberrations. Much of this is sagittal flare, overlaid by chromatic errors.
The question below was asked in regards to the 18/3.5 Distagon, but also applies here, even more so due to the faster f/2 aperture of the 28mm f/2 Distagon.
DIGLLOYD: Can we expect to see any strange "shapes" for point sources near the edges/corners of the frame wide open as is seen with the 28/2 Distagon?
Zeiss: 'Bird wings' are of course much less visible compared to the 2/28 due to the more moderate speed. This is already indicated by the MTF-curves: 'bird wings' mean sagittal flare, and this is expressed in a considerable drop of low frequency MTF towards the corners. This is not the case with the ZF18. Please compare the psf-bitmaps.
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Diglloyd Guide to Zeiss offers comprehensive integrated coverage of Zeiss DSLR lenses for Canon and Nikon. Nearly a decade in the making, it covers everything you need to know for every lens in the ZF.2, ZE, Milvus and Otus lines. Guide to Mirrorless and Zeiss ZM rangefinder lenses in Guide to Leica.
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