Re: Exact fl of lenses... 220 VR

[Gene Woolridge <gene360@xxxxxxxxx>]

Bill,

        I would love to have Peter Seitz read this post to see if he agrees
with your findings. ( Just to have someone give us a definative answer. We all
have better things to do than RE-INVENT the wheel!)

No snip intended, in case someone gets offended.

Bill Glickman 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