On Thu, Apr 18, 2002 at 09:40:39AM -0700, Dave Shupe wrote:
> I am nearsighted (-2.0) with a slight astigmatism. I've noticed lately that
> I can focus my binoculars at any distance, and see sharply without my
> glasses. My question is, why can't I focus the camera the same way.
>
> I understand why it would not be good to do so, kind of like handing the
> binoculars to someone with good vision, they have to refocus. Therefore If
> I could focus without glasses my pictures would be blurry. Just wondering
> how the camera focus system actually works.
This is my idea to this topic:
The mate-part of the focusing screen forces your eye to focus
the picture of the lens on the level of the film plane. With your
binoculars it doesn`t matter in which plane you can see the image.
Because of that there is no need for a mate-sreen in the ray path
of a field glass. One focusing mechanism is sufficient to compensate
for distance and eysight differences.
With a clear screen (1-5; 1-6; 1-7) your eye can see a sharp image
of your subject which is not in the propper distance. I guess this is
why you can only focus with the microprism area when using this screens.
Just my thoughts.
Frieder Faig
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