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[OM] Re: E-1 craving

Subject: [OM] Re: E-1 craving
From: Dan Mitchell <danmitchell@xxxxxxxx>
Date: Fri, 11 Aug 2006 08:13:31 -0600
> Okay, if we're talking about, for instance, my RB-67 and using the
> eye-level prism finder, in acuality, you're just looking in a little
> window, through a prism, and at the very same piece of groundglass
> you look at when using the waistlevel finder, except now you can only
> see it with one eye. What about that could possibly make it brighter?
> It appears the same size, and, in fact, since there's more glass
> involved, it's probably a little dimmer.

  So the ground-glass focus screen in a 120mm camera is also larger than 
in a 35mm screen, right? (it must be, or the mirror would have to be 
curved to shrink the image down, I guess).

  And so the light-per-area on the focus screen is thus the same as that 
on a 35mm screen, and there's more focus screen area -- but because the 
entire camera is physically larger, my eye has to be further from the 
screen on a 120mm camera than it is from a 35mm screen, so because of 
distance falloff the final percieved result is the same. (and I guess 
the eye relief lenses don't make any difference here; they just change 
where I need to focus my eyes to see it, the amount of light is the same).

  I think that makes sense..

  -- dan

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