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Re: [OM] eyesight vs. focusing

Subject: Re: [OM] eyesight vs. focusing
From: Ken N <image66@xxxxxxxxx>
Date: Thu, 9 Aug 2001 10:55:19 -0700 (PDT)
> This didn't sound right, so I checked out some old Modern
> Photography tests of OMs. One of the things they measured was
> the apparent viewing distance of the screen and the displays. 

There is a clue to this that immedietly caught my eye:

> OM-4T apparent viewing distance: adjustable between 13 inches
> and 39

I'm not an optical expert here, but the diopter shouldn't change
apparent viewing distance.  MP's tools for measuring distance
were incorrectly applied to the test.  If this were true, then a
+3 diopter should change the apparent viewing distance to a few
hundred meters!  My eyes aren't THAT bad without glasss.  

If MP's tests were true then my eyes would need to refocus
(farther/closer) everytime I looked over the tops of my eyeglass
rims. As I'm typing this, The computer monitor is almost two
feet infront of my schnoz (nose). With my glasses slipped down a
bit I can easily compare with and without glasses.  My eyes are
not refocusing when I go back and forth.  With glasses I can see
the screen better, but my viewing distance still remains the
same.

Not scientific, I know, but I've "dual-eye" tested my
viewfinders by looking through the camera with one eye and
keeping the other open and see at what distance both eyes are in
focus.  With my OM bodies, with and without diopters, my focus
point is approximately FIVE feet (just under 2 meters). 
Repeating the test with the other eye at the viewfinder resulted
in almost identical distance.

I performed this test with a 35-70 zoom and the camera tripod
mounted.  I took great care to match subject size and position
in the viewfinder to my open eye.  I even varied the alignment
to counter any eye-focusing based on astigmatism.

I'd like to know from our optical expert (Hello Susan), on how
eyeglasses can change apparent distance.

Ken N.

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