Exact fl of lenses... 220 VR

[Bill Glickman <bglick@xxxxxxxx>]

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