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Forum: Pentax SLR Lens Discussion
04-06-2016, 09:57 AM
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V-A-V the comments above. It is true the human eye does not see things in rectilinear perspective, but our minds make images appear that way. Whether the rendering by a lens has "natural" perspective depends on where you place your eyes relative to the image. For a fisheye lens rendering of a scene, to make it look "natural" (= as your eyes would see it) you need to view the image from a matter of inches away, for example, you'd need to place your face almost on top of a computer screen turning slightly so your nose did not touch the screen in order to see an uncropped fisheye image in "natural" perspective. Fisheye lenses can/do serve two or three purposes: 1) to include far more of a scene than is possible to record with a single shutter click with any other lens; 2) to use fisheye distortion as a creative element; and sometimes, possibly 3) to obtain enormous DOF. A stitched panoramic covering 180 degrees horizontally looks very different from a fisheye rendering of the same scene because of, well, fisheye distortion.
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Forum: Pentax SLR Lens Discussion
04-06-2016, 05:30 AM
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I looked into the Zenitar but never owned one (have owned three other fish-eyes). My impressions from reading numerous reviews: 1) obviously much less than 180 degree coverage on APS-C, coverage probably less than a Sigma 10~20 @ 10mm**; 2) center sharpness marginal @ f2.8 but improves significantly @ f4, and more at smaller apertures; 3) edge sharpness dismal @ f2.8 and improves very gradually; 4) best overall IQ @ f11 or 16 where it is quite good edge-to-edge; 5) at least some versions have a manual diaphragm = you must twist the aperture ring to stop down after focusing but before using the green button to set exposure; 6) very difficult to focus = take advantage of the enormous DOF at small apertures (f11~16) and guestimate the hyperfocal distance, or better: make a test run at different focus-distance settings on the focus ring and take notes on a card to carry along, unless your memory is better than mine (not difficult).
**On an APS-C body although you'll get far less than the 180 degree coverage, you will get the fish-eye barrel effect IF that is what you're after.
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