At 10:25 AM -0600 2/8/07, Larry wrote:
> I'm fairly new here so perhaps this is a bit off-topic, but I've
actually got a question about an EOS camera. :) I'm contemplating
buying a 5d, which seems like a pretty good deal with Canon's $600
rebate on top of B&H's low price.
The annual PMA (Photo Marketing Association) show occurs, I believe, in
early March. New products are commonly introduced there, and often announced
a week or two before the show. That's close enough that I would wait to see
if anything is announced and if not, then I'd buy the 5D. Even if a 5D
replacement is introduced and you decide the 5D is good enough, its price
would likely drop further after such an announcement.
Another matter discussed earlier this week was the size of EOS lenses. One
reason for the larger lens mount is to be able to design and produce faster
(larger aperture) lenses.
Several years ago a Japanese magazine quoted a Nikon engineer as explaining
that Nikon could not produce autofocus versions of their 50 f/1.2, 35 f/1.4,
24 f/2 and similar fast lenses because the rear elements completely filled
the available space and there was no room for AF contacts.
A larger throat diameter at the lens mount makes the designer's job
easier, but it is not an absolute necessity. In any case, there's the
28/1.4 AF Nikkor, which by all accounts is a pretty decent piece of
glass.
Probably the 50/1 would be the most difficult to design, but even
would be possible. One of the other parameters that might have to be
stretched is cost, as in very expensive special glass types.
With a larger
lens mount and larger lenses, Canon does not have this limitation and has
produced fast AF lenses we Nikon users can only envy.
(I've often wondered if Nikon couldn't compensate for the rear element
limitation with larger front elements to gather more light. But I don't know
enough about lens design to know if that's possible. And the bottom line is
that the EOS system has fast lenses which the Nikon AF system lacks.)
A large part of the equation is the positioning of the company, and
where it feels its efforts are best placed. Nikon lacks a couple of
focal length/speed combinations that Canon has, while Nikon has some
wideangle lenses with optical qualities that Canon user's can't
access. No manufacturer has everything covered and excels at
everything.
Larger front elements help with vignetting, while sometimes
exacerbating other optical faults. To reduce the size of the rear
elements, sometimes more elements are needed, or higher index or
other special glasses or possibly additional aspheric elements.
--
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:[EMAIL PROTECTED]
|[ ]| http://www.archiphoto.com
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