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Re: [OM] Infinity focus & focusing screens

Subject: Re: [OM] Infinity focus & focusing screens
From: Donald Shedrick <shedridc@xxxxxxxxx>
Date: Sun, 20 May 2001 18:10:56 -0700 (PDT)
I must have not been clear in my explanation.  I took
2 shots with each lens - one with the 1-13 screen
(using the split image on a vertical building edge),
and one with the 1-8 screen (focused on the matte in
the center circle) - each focused for best focus on
the distant buildings as indicated by the respective
screen.  Varimagni finder was used at the high
magnification position in all cases.  With all lenses,
the split image screen resulted in the best focus
point as seen through the finder being slightly less
than the infinity symbol, and the matte screen
resulted in the best focus point as seen through the
finder being at the infinity symbol.  With all lenses,
the screen which gave the best focus on the slide was
the 1-13.  The slide using the 1-8 screen was slightly
out of focus. 
After thinking some more about this, I think the matte
screen is more sensitive to the different focus points
of different eyes.  Have you noticed how someone else
using binoculars or a telescope will foucs them, and
when you look through them, they are slightly out of
focus for you?  However, the split image screen is
using a technique of lining up of two images, which
may not be as different for different eyes.  I guess
we all have to get diopter correction lenses in our
eyecups so we can obtain accurate focus, and not focus
the camera to compensate for our eye.
My conclusion is use a split image screen for most
accurate focus unless you have corrective lenses in
your eyecup.  Thoughts?


--- Gary Reese <pcacala@xxxxxxxxxxxxx> wrote:
> Hi Donald:
> 
> Thanks for posting the results of your test.  You
> didn't mention the
> results from a re-do of the 1-8 screen.  Still
> getting best focus at
> infinity?
> 
> Can I surmise that you have the same conclusion I
> do: use an all matte
> screen for most critical focus?
> 
> Gary Reese
> Las Vegas, NV
> 
> 
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