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RE: [OM] Why is the 50mm the brightest lens?

Subject: RE: [OM] Why is the 50mm the brightest lens?
From: "Daniel J. Mitchell" <DanielMitchell@xxxxxxxxxxxxx>
Date: Tue, 31 Jul 2001 10:08:23 -0600
>Not sure what you mean by "least" amount of glass. Other things
> being equal the faster the lens is the more glass it will have 
>in order to allow  more light to get in. There's no reason the 
>40mm f2 could not be an f1.2, though with cost in terms of its 
>size and weight--if that lens were an f1.2 it would come to us
> looking an awful lot like the 50/2.

 Okay, so I'm obviously confused about something. I was assuming that the
shorter the lens, the less glass there would be between the outside world
and the film, so there would be less light reduction because the light is
passing through a smaller amount of stuff. Though that, of course, is
forgetting that faster lenses tend to be bigger at the front, which
obviously lets more light in..

 But I'm still not sure why it is that the 50mm lens is the fastest -- is it
just that there's not the demand for a $100,000 300mm f1.2 lens? Is it just
the case that 50mm lenses happen to match up to 35mm film in a particularly
handy way to allow making fast lenses at that size without it being too
expensive?

 -- dan (perhaps I should just get a book on optics and this would all
become clear..)

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