On 11 Mar 2001, at 10:10, [EMAIL PROTECTED] 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."
Hi Paul,
Rectilinear lenses should all provide the same projection on the film plane, it
they did not then straight objects placed at the edge of the frame would be
rendered curved. Therefore all well corrected rectilinear lenses should provide
the same degree of subject elongation. The fact that the better SLR wide
angle lenses (particularly pre-aspheric) tend to be long is due to their
retrofocus design which is by all means a compromise designed to make
available space in front of the film plane for the SLR mirror to swing.
Don't kid yourself about SLR wide angle lenses, for real no compromise
designs check out the Leica-M, Contax-G and Mamiya RF designs, most
are virtually symmetrical designs and have a magnitude lower distortion than
the best retrofocus wides, many are designed such that their rear elements
are merely mm from the film plane. :-)
Cheers,
Rob Studdert (eBay ID: distudio)
PO Box 701
HURSTVILLE BC NSW 1481
AUSTRALIA
Tel +61-2-9554-4110
Fax +61-2-9554-9259
UTC(GMT) +10 Hours
[EMAIL PROTECTED]
Please check my current eBay auctions:
http://www.ozemail.com.au/~distudio/ebay/
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