on 2/4/02 6:45 AM, Jez.Cunningham@xxxxxxxxxx at Jez.Cunningham@xxxxxxxxxx
wrote:
> <Putting on Nomex>
> What do folks think about a 19-35 zoom for occasional use?
> If only there was a Zuiko...
> jez
Sure depends on how often you are going to use those focal lengths, and what
kind of subjects. For buildings, where any barrel or pincushion is going to
be noticable I'd be wary, but if you only take 2 pictures of buildings a
year (exaggerated example) then it is hard to justify a 24-shift or 18/3.5
lens. On the other hand, I have one of those Samyang 18-28 zooms and it
seems to be pretty well constructed. I have only one image made with the
lens, and it looks OK (just a quick grabshot of my living room). I think for
landscapes, nature pictures, waterfalls, etc. where there aren't many
straight man-made lines, even a lens with some 'distortion' can be used.
Note that *any* wideangle lens giveing rectlinear images is going to have
'distortion' compared with a true human eye view, but we humans do a *lot*
of image correction 'in software'. The full-frame fisheye is most true to
the image our eyes actually see, but then the image plane of the eyeball is
curved hemispherical, so the 'distortion' is mapped out at the image plane.
The 'distortion' of the superwides is related to mapping a 3-D image onto a
2-D image plane and is inherent in the process. I believe it is progressive
with focal length, hence a 21 lens will show more 'distortion' (mapping
artifacts) than a 24 lens for the same image. For the same subject size on
the film, the 21 will be closer to the subject, so the extreme corners of
the image (where 'distortion' is greatest) with be at a more acute angle to
the film plane, hence more 'distortion' is evident.
If you could use a curved hemispherical film plane with a lens designed
accordingly then an extremely wide field of view could be achieved without
'distortion'. Some cameras for panorama images use curved (cylindrical
section) filmplanes and moving lenses that 'map' the wide field image onto
the film, so the 'distortion' is minimized in one direction. A careful
panorama setup will allow images that can be stitched to get the same
result.
--
Jim Brokaw
OM-1's, -2's, -4's, (no -3's yet) and no OM-oney...
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