Just a little additions and a few pondered thoughts:
Concerning the DOF, for a 300mm lens on a 35mm frame, it turns out that you
have to focus on a subject set at least at 10m before getting 1m of DOF at
f/16.
If you look at the donut highlights in the background you can see that they
progressively get less 'blurred' as you stop down the lens. Their size, and
the size of the black center circle, however, doesn't change with the
f/stop.
This leads me to think that the lens should have a diaphragm or the like of
it.
Other opinons are welcome
Ciao!
Fabio
On 7/14/06, Fabio Fiorellato <flowerside@xxxxxxxxx> wrote:
>
> I had the same feelings.
>
> It's undoubtable that the donut-shaped bokeh is a real cr*p.
>
> Anyhow - if my eyes aren't fooling me - I can see small DOF differences in
> the test shots. Maybe the not-so-prononuced DOF differences are a
> consequence of the tester being very near to the focused subject?
>
> After all we're talking about a 300mm lens which is supposed not to have a
> huge DOF especially at short distances.
>
> Of course, these are just my humble suppositions: I too was wondering
> about how could it be possible to build a variable-aperture CAT...
>
> Ciao!
>
> Fabio
>
> On 7/14/06, Moose <olymoose@xxxxxxxxx> wrote:
>
> > Fabio Fiorellato wrote:
> > > What about this CAT?
> > >
> > > [ http://homepage3.nifty.com/3rdpartylens-om/ohnar300.htm ]
> > >
> > > and
> > >
> > > [
> > http://homepage3.nifty.com/3rdpartylens-om/Lens%20Test/ohnar300test.htm]
> > >
> > > So far, it's the only one I know with variable aperture!
> > Doesn't look like it's really variable aperture. Looks more like it may
> > have built in neutral density filters, convenient, but not at all the
> > same thing. The reason I say that is that the DOF doesn't change from
> > f5.6 to f16. With a true aperture change, the DOF would change a great
> > deal over that range.
> >
> > We've had discussions about whether, and how, variable aperture with a
> > mirror lens might be possible. Looks like nobody has yet figured it
> > out. :-)
> >
> > Still has that donut bokeh, particularly awful in the demo shots.
> >
> > Moose
> >
> > ==============================================
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> >
>
>
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