EXCERPT page containing first few paragraphs. 2019-06-24 05:47:10
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This series with full 12mm fall (downward shift) along the long axis shows just how critical it is to focus the Nikon 19mm f/4E ED PC-E PC-E in order to balance out the field curvature—f/11 does not overcome the behavior.
Shot prior to discovering field curvature issues, this example is excellent in showing what naive choice of focus would deliver. Focus was off only because of the difficulty of discerning peak focus at f/4—the smart move is to scroll in Live View nearer and farther to verify that the zone of focus is where intended—I forgot to do this—f/4 has enough depth of field to make peak focus somewhat ambiguous in dim light.
Also discovered here is a pronounced rearward focus shift, which is even more important than the field curvature of the outer zones.
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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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