Hi,
I am not Rob but I think he's right.
I my (also limited) understanding the elongation of
objects near the edge of the image produced by
rectilinear super wide angle lenses is not related to
optical aberrations of these lenses. It is inherent in
how the image is projected on the film by these
lenses.
To avoid this you need a "cylindrical projection"
(with the viewer in the center of the cylinder) as is
provided e.g. by the Seitz roundshot camera.
Also fish-eye lenses do not show such kind of
elongations of close subjects near the edge.
Alexander
Mike Johnston wrote: --------------------------------
Rob,
A longer barrel--such as that used on the SMC 28/2,
which was designed with
Zeiss--can bend the rays more "gently." Isn't extra
barrel distortion one
of the compromises usually introduced by a shorter
lens (unless, perhaps,
an aspherical element is used)? Isn't that why "no
compromise" lenses are
typically longer, and use more elements? Or do I need
to brush up on my
limited understanding of Cartesian optics?
PS: Of course, every lens design is a compromise. By
no-compromise, I mean
to suggest "the best a lens maker has to offer."
"Rob Studdert" <[EMAIL PROTECTED]> wrote:
Subject: Re: 28/2-class lens specs: Seven Third-Party
Lenses vs. Three
Pentax 28/2s (was: Re: fast kiron on ebay)
On 10 Mar 2001, at 19:20,
[EMAIL PROTECTED] wrote:
> To my eye, 28mm is the widest
> practical focal length for "people-shooting," which
is what I do. True,
it
> makes people at the edges of the frame look fat. But
this problem is
> minimized by selecting a well-corrected prime.
Hi Paul,
Please explain, to my mind there should be a similar
degree of perspective
distortion present (ie elongation of close objects at
the edge of the
frame) in
any well corrected optic. The only way that I can
imagine that there would
be
differences is if the lens that looks more normal has
a semi-spherical
plane
of focus?
Cheers,
Rob Studdert
HURSTVILLE AUSTRALIA
Tel +61-2-9554-4110
Fax +61-2-9554-9259
UTC(GMT) +10 Hours
[EMAIL PROTECTED]
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