EXCERPT page containing first few paragraphs. 2020-09-19 11:32:03
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This medium distance scene assesses field curvature, with clear-cut definitive results.
All wide angle designs of f/2.8 or faster speed of all brands have significant to substantial field curvature. Field curvature results from the natural Petzval field curvature inherent to lenses.
With an f/1.4 design, balancing field curvature against other aberrations is quite difficult. This is why wide angle lenses are just never free of some field curvature, particular f/1.4 and f/2.8 designs, but even f/2.8 designs still exhibit some field curvature.
Example — fence
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Diglloyd DAP is DSLR-oriented, but also contains workflow and other topics. Much of the focus is on Canon and Nikon but also Pentax and Pentax medium format.
Special emphasis is placed on lens evaluation, focusing on Canon and Nikon and Sigma lenses, but with a few others like Rokinon/Samyang.
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- Optical quality analysis of field curvature, focus shift, sharpness, flare, distortion, and performance in the field.