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EXCERPT page containing first few paragraphs. 2023-03-29 05:38:28

Zeiss Touit 12mm f/2.8 Distagon

Field Curvature Analysis (Alpine Creek, Sony NEX-7)

This example shot on the 24-megapixel Sony NEX-7 (6000 X 4000). See the other examples taken under the same conditions.

Understanding field curvature behavior of a lens is key to extracting maximum image sharpness for any particular “shape” subject for that lens: choice of focus position can work for or against total image sharpness in a very substantial way. Stopping down is never a panacea, even with a 12mm lens.

See Making Sharp Images for a general discussion of field curvature.

What the MTF chart suggests

The MTF chart for the 12/2.8 Distagon shows that the edges and corners are less sharp than the central areas, particularly wide open. That said, these curves are among the best one might find for high-end 18mm (equiv) lenses. The difference between f/2.8 and f/5.6 is actually quite small most of the way to the edges— very high performance wide open.

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Want a preview? Click on any page below to see an excerpt as well as extensive blog coverage, for example on Sony.

Aperture series 2.8, 5.6 available in full article
Zeiss Touit 12mm f/2.8 Distagon MTF
f/4 @ 1/80 sec handheld, ISO 200
Sony NEX-7 + Zeiss Touit 12mm f/2.8 Distagon

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