Bob Atkins has written a nice introduction called: "Wide angle lenses for
small sensor APS-C Digital SLRs" that compares the new lenses from Tamron,
Tokina, Canon, and Sigma. A second page adds thoughts on fisheyes. He also
offers a review of the Zenitar with example photos!
http://www.bobatkins.com/photography/reviews/wide-angle-lenses.html
Not many of the new APS-sized wide lenses are actually available yet,
especially not in a Pentax mount. This includes the Pentax 12-24mm that was
announced in March (I was wrong there).
Does 1-2mm matter? I don't know, I guess other things will influense your
choice more than whether the lens is 10, 11 or 12mm at its widest. What do
you think?
The other thing to note (that the atkins article mentions) is that
the conversion from fisheye-rectiliner isn't a simple geometric
transformation. The fisheye is effectively wider (i.e. will cover
more angle of view) than an equivalent rectilinear lens, although it won't
do so consistently throughout the frame. In other words, converting to
rectilinear loses a lot of image in the corners of the fisheye image.
In other words, they're completely different. If you can get away
with the barrel distortion from a fisheye, you'll tend to get better
results than trying to defish it all the time.
-Cory
--
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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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