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From: ron@brl-tgr.ARPA (Ron Natalie )
Newsgroups: net.rec.photo
Subject: Re: viewfinder intensifiers
Message-ID: <8199@brl-tgr.ARPA>
Date: Sun, 10-Feb-85 18:12:18 EST
Article-I.D.: brl-tgr.8199
Posted: Sun Feb 10 18:12:18 1985
Date-Received: Wed, 13-Feb-85 03:12:44 EST
References: <512@hou5g.UUCP>
Organization: Ballistic Research Lab
Lines: 25

> I'm interested in squeezing a little more light out of my medium format's
> viewfinder. I've seen Beattie's Intenscreen but at $130 I wonder if
> there are alternatives. For example, there's another company that for
> $60 will lamenate (?) a fresnal screen onto your own viewfinder screen.
> That way, you can keep whatever type of screen you currently have
> (e.g., split image).
> 
> Has anyone tried doing this themselves? Edmund's sells fresnel lenses -
> but I'm confused about the fresnel lens' focal length rating. How should the
> f.l. be mounted to the viewing screen? Is there a danger of getting the
> focus point out of kilter?
> 
> Also, has anyone used these intensifiers? Do they have "hot spots"?
> 
> Thanks in advance.			-Rich

I don't understand this at all.  Is it that applying the
lens directly to the screen is collimating the light from the screen?
It would seem that you aren't simply magnifying the screen since you
are attaching the lens directly to the screen.  In any case, I don't
believe that you can get the focus out of kilter unless you actually
change the focussing screens position.  Any lenses that you add between
your eye and the screen don't affect what is projected on the screen.

-Ron