Didn't someone here claim the 20mmF2 macro was diffraction limited at F2?
Quoting Thomas Heide Clausen <T.Clausen@xxxxxxxxxxxx>:
> 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.
> >
> >
> >
> > < This message was delivered via the Olympus Mailing List >
> > < 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
> -------------------------------------------
>
> < This message was delivered via the Olympus Mailing List >
> < For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
> < Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
>
>
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|