Thanks Moose,
The longer lenses generally had higher resolution numbers quoted which
is of course is related to subject size via focal length. I was
wondering not about magnification of the subject but if there was
something about mirror lenses which would make it easier to design a
longer lens which gives higher resolution at the film plane.
Since the mirror lenses don't suffer significantly from chromatic
aberration which seems to be worse for longer focal lengths, they might
have some other aspect which makes longer focal lengths have higher
resolution at the film plane. I vaguely remember something about
resolving power of telescopes increasing with either mirror diameter or
focal length but that again was related to the subject rather than the
accuracy of the image at the film plane.
-jeff
----- Original Message -----
From: "Moose" <olymoose@xxxxxxxxxxxxx>
> Jeff Keller wrote:
>
> >Easy question - does the Sigma 600/8 use a T adapter or did they make
> >camera specific mounts?
> >
> Camera specific.
>
> >If the lens resolution is measured at the film plane image it's not
> >obvious to me why a longer lens would have a higher resolution.
> >
> I wasn't disagreeing with the published resolution numbers, just
> pointing out how the standard tests aren't entirely relevant for some
> super-tele photography. The standard tests reproduce the test chart at
> the same size on film regardless of the focal length, the right way to
> measure inherent resolving power. In using super-teles, I often find
> that I can't magnify the subject to fill the frame from the vantage
> point I have and can't move closer. In that case, there is no loss of
> desired image coverage from using a longer lens, but the greater
> magnification resolves greater detail in the subject.
>
> With a 1000mm lens you
> can see detail in the target for about twice the resolving power as
> those that could be distinguished by the 500mm. It's not a resolving
> power factor is the traditional sense, but has that effect through
> different magnification a the particular kind of situation.
>
>
> Moose
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