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[OM] Re: E-1 craving

Subject: [OM] Re: E-1 craving
From: Moose <olymoose@xxxxxxxxx>
Date: Thu, 10 Aug 2006 21:14:31 -0700
Chuck Norcutt wrote:
> No, regardless of the size of the viewfinder and a whopping big mirror 
> you can't have a really bloody bright viewfinder with an f/4 lens.
>   
As a matter of theory, I'm not sure I agree. Although the brightness per 
area is the same with the same speed lens, the total amount of light on 
the focusing screen is greater. So when concentrated into the same size 
visual image, the larger format camera, with same speed lens, should 
have a brighter image.

As you say, MF lenses tend to be slower, but the factors should more or 
less balance out, in theory.

I suspect this in not true in practice because of compromises in the 
design of MF viewfinders. I suspect the problems of size, weight and 
cost go up with something like the cube of the film diagonal with 
pentaprism finders. The penta prism is much bigger and the eyepiece 
optical system has to cover a much greater area. The eyepieces are 
probably also slower for size/cost reasons.

Moose

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