EXCERPT page containing first few paragraphs. 2018-11-18 05:11:30
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According to lens designer Brian Caldwell:
The coma and oblique spherical disappear quickly on stopping down, which is why performance in the extreme corner suddenly gets great at f/8.
If the problem were truly field curvature then the improvement would be much more gradual.
The latter statement is true, but field shots suggests a very mild field curvature at inifinity focus which “piles on” its subtle effects when shooting the 60/4 at infinity. Use of f/8 is strongly advised for peak quality on high-resolution digital.
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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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