I think it has something to do with diffraction, i.e. some physical
properties of light entering through a "small enough hole". However I
am sure that we have someone on the list who are much more capable
into optics and physics than me, so I will not pretend to know a
whole lot on the how and why of that.
However......this is what I know on the topic...
I read somewhere about that good lenses have an optimal
apeture from which they are "diffraction limited". I.e. that
diffraction is the singlemost important degrading factor of a lens -
meaning that a lens couldn't get better (since diffraction is a
result from a law of physics, not something a lens producer can fix
by designs and coatings - contrary to e.g. flare and chromatic
abbreation). The very best such lenses should be "diffraction
limited" at their full apeture (I've only ever heard of enlarger
lenses that claimed to be diffraction limited at full apeture, but
then again, I am not an optical engineer), whereas most (i.e. those
we can afford) are diffraction limited at some smaller apeture. I
have a Pentax 77mm/1.8 limited, which is said to be quite good at
that respect: I've read that it is "diffraction limited" from when
stopped down 1/2 stop or so.
I have no idea how true the above is (so please feel free to
enlighten me), if it is true how to measure/test it. And I have no
clue how our beloved Zuiko glass test in this respect.
Was that as close to a non-answer as possible? :)
--thomas
On Wed, 05 Feb 2003 17:55:14 +0000
Roger Wesson <roger@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
> There's an inverse relation between the size of your aperture and
> maximum theoretical lens resolution. The smaller your aperture the
>
> coarser your best possible resolution becomes.
>
> Roger
>
> R. Jackson wrote:
>
> > Really? I wasn't aware of that. Do you know why that occurs?
> >
> > -Rob (big fan of Group F64)
> >
> > On Wednesday, February 5, 2003, at 01:40 AM, Winsor Crosby
> > wrote:
> >
> >> 35mm starts to soften at F16 or F22.
>
>
>
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> < For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
> < Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
>
--
-------------------------------------------
Thomas Heide Clausen
Civilingeniør i Datateknik (cand.polyt)
M.Sc in Computer Engineering
E-Mail: T.Clausen@xxxxxxxxxxxx
WWW: http://www.cs.auc.dk/~voop
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