On Wed, 30 Oct 2002 12:50:26 +0000, David Littlewood wrote:
>In article <3c459ba.0210300130.4af4dacf@posting.google.com>, brian
> writes
>>David Littlewood wrote in message
>>news:...

>>> Brian, my comment was a general one and not based on any contact with
>>> the particular lens. I suppose I should have known better than to get
>>> involved in a Nikon thread!
>>>
>>> On a more general note, yes it is true that (most) larger format lenses
>>> have lower resolution figures (I suspect those on my Mamiya 6 come
>>> pretty close though). This has always puzzled me; simple logic suggests
>>> that if you simply scale up the design it should give similar results. I
>>> appreciate this might be mechanically difficult, but I do wonder if an
>>> element of "we only need to build to the spec required and no more"
>>> comes into it. As you have a background in lens design, perhaps you know
>>> why this difference exists?

>>Hi David:
>>If you simply scale up a design the aberrations will increase by
>>exactly the same amount. If these aberrations remain small relative
>>to the Airy disc (diffraction) then the performance will be similar,
>>but in photography this is rarely the case and performance in terms of
>>MTF or resolution will be significantly worse in the scaled up design.
>> Some of this drop in performance can be recaptured by re-optimizing
>>for more modest specs, such as a smaller aperture.

>Duh! Must have been the middle of the night when I asked that, it's
>quite obvious when you say it.
>
>Thanks anyway, Brian.

There are exceptions, where the scaled-up lens (and
coverage) do not affect performance much (most of the Nikkor
PCs are good examples - well the latest 35mm f2.8, and
the early 28mm f4, anyway...;-), like the Kodak 203mm f7.7
view camera lens, lots of the best 2 1/4 lenses, etc. - but
there generally is a sacrifice in speed or in something
else like coverage (many older "telephoto" lenses were
similar to wide-coverage optics, but redesigned to perform
better over the smaller angle recorded on smaller film
formats), as Brian noted...

>As it happens, I think my Canon 24 TS-E is an excellent lens, which
>suggests Canon did a good job on it, but I've never done any structured
>tests on it.

It is an excellent lens, from what I've seen of its
images... (I also liked the AF Canon 24mm f1.4, listed
at: www.David-Ruether-Photography.com/slemn.html [a Nikkor
list ;-]).