Shipman, on page 66, states: "With long focal length, narrow angle
lenses, the image is nearly full size at the mirror location.
Therefore, a relatively large mirror area is required to intercept the
rays and reflect them up to the focusing screen. In some camera
designs the bottom edge of the mirror is shortened so the edge
doesn't collide with the camera body or the back of the lens when it
swings up. When this is done, part of the image cast by the long
focal length lenses is not intercepted by the bottom of the mirror
and therefore is not reflected up to the focusing screen. THe
bottom of the image on the mirror becomes the top of the image in
the viewfinder. With most models what you see with long lenses is
a dark band across the top of the focusing screen with part of the
image lost in the dark band. This is sometimes called image cutoff.
Even if it happens in the viewfinder the image on film is not affected
and not cut off because the image on film is not reflected by the
mirror. All camera designers face this technical problem. Olympus
solved it by shortening the bottom of the mirror only a small
amount so image cutoff happens only with very long focal lengths
such as 1000mm. In the specs, this is referred to as an oversixe
mirror." Too, the OM PC only shows 930f field vs. 970n OM 1.
Perhaps its mirror is a bit smaller which would highten this
situation. --Greg
Date sent: Fri, 2 Apr 1999 01:02:12 -0800
From: owner-olympus-digest@xxxxxxxxxxxxxxx (olympus-digest)
To: olympus-digest@xxxxxxxxxxxxxxx
Subject: olympus-digest V2 #848
Send reply to: olympus@xxxxxxxxxxxxxxx
> Date: Thu, 01 Apr 1999 16:23:11 +0200
> From: "Marco Tomat" <tom@xxxxxxxxxxxx>
> Subject: R: [OM] OM-40 (OM PC) and the 1000mm lens?
>
> This is true of the 250/2, 350/2,8 and 600/6.5. Not in program mode I mean
> (instructions, p. 73). But why not the 1000/11? Maybe you don't see much in
> the viewfinder? Maybe who has experience with that 4 Kg lens can say why...
> This looks a perfect excuse for not buying such expensive glasses: "You
> know, I *cannot* use them on my sophisticated OM-PC!"
>
> Marco
>
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