Re: Exact fl of lenses... 220 VR

[Bill Glickman <bglick@xxxxxxxx>]

Andy

         I don't enjoy this.... but I wanted the best possible images, so I
followed the instructions of the inventor, Mr. Seitz....  I kind of agree
with you, but thats not the way it is..... a users group sure would help, we
could document everyone's findings and share them.

       To be fair, there are some lenses such as Nikor , and Hassy that have
numbers  listed in the manual.  Of course they still should be tested due to
variance in manufacturing, but it sure would be nice to have a close
starting point!    But no values for my mamiya lenses.  Whats worse it there
a Mainplane number the brain box requires for each lens, used when shooting
things close.  The only place to get this value is from the lens makers.
The Sietz's have not gotten it, and either have I.  It seems Mamiya won't
release it.  My question is, then why do they sell a  Mamiya mount and
promote those lenses???  No one has answered that one yet.

Regards
Bill G


> All this work just to figure out how to use a camera
> that costs *that* much? Unbelievable. For that much
> money, I'd expect to set it up and use it, or at
> least, find complete instructions and charts included.
> IMMHO!
>
> --- Bill Glickman <bglick@xxxxxxxx> wrote:
> > 220 VR users:
> >
> > Here is the results of my testing....
> >
> > After extensive testing I have concluded the
> > following... I would hate for
> > anyone to have to go through 60 rolls of film like I
> > just did.
> >
> > Mr. Seitz says that one needs to determine the exact
> > fl down to .05mm for
> > images to be sharp.  As I mentioned in prior posts,
> > I felt the best way to
> > accomplish this was shooting a building with a known
> > aspect ratio and then
> > match this ratio on film.
> >
> >       I succesffuly accomplished this down to .1mm
> > per lens.  However, I was
> > suspicious if under different rotational speeds the
> > same exact fl would hold
> > true.  It would take some really precisioned motor
> > gearing for this to
> > occur.    For example, at 1/15 speed, my 150mm lens
> > computed consistently
> > out to be 146.3mm.   However at 1/125, the lens
> > computes out to be 149.0mm.
> > So, as you can see, to have an exact fl for a lens,
> > one must test this for
> > each shutter speed.  Then enter into your brain box
> > the fl value that
> > matches the shutter speed selected.  In other words,
> > you would need about 9
> > exact fl values for each lens to be sure you are
> > accurate, at any shutter
> > speed.  (to be fair, I did not test at all ss, just
> > a few, but the pattern
> > was obvious)
> >
> >       So all my testing was in vain, because at
> > different shutter speeds the
> > exact fl varies ... I can't spare 2 weeks and  200
> > rolls of film to figure
> > this out for each shutterspeed.  Therefore, to me,
> > it does not make sense to
> > try to nail each fl so exact, unless you are willing
> > to do it for every
> > shutter speed you plan to shoot at.
> >
> >          So for me, its boiled down to an
> > estimate....  Sure wish this was
> > in the manual?  Bottom line, .05mm is a unrealistic
> > goal, and even .1mm will
> > only reproduce itself at the shutterspeed it was
> > tested at.
> >
> >       Anyone have a different experience?
> >
> >       I also tested different film speeds and the
> > auto exposure... the auto
> > exposure it apperas requires much tweaking to
> > prevent banding.  As for the
> > different shutter speeds, at 1/250 and sometimes
> > 1/125, uneven film uptake
> > can be seen... It seems best to shoot at slower
> > shutter speeds...
> >
> > Hope this can benefit some users....
> >
> > Regards
> > Bill G
> >
>
>
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