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From: darrelj@sdcrdcf.UUCP (Darrel VanBuer)
Newsgroups: net.rec.photo
Subject: Re: f/1 lenses
Message-ID: <1923@sdcrdcf.UUCP>
Date: Mon, 22-Apr-85 22:45:36 EST
Article-I.D.: sdcrdcf.1923
Posted: Mon Apr 22 22:45:36 1985
Date-Received: Thu, 25-Apr-85 03:08:12 EST
References: <2720027@acf4.UUCP>
Reply-To: darrelj@sdcrdcf.UUCP (Darrel VanBuer)
Organization: System Development Corp. R+D, Santa Monica
Lines: 29
Summary: 

The few f/1 lenses I've seen or heard of (excluding things like fresnel
burning lenses which don't need high resolution) were all rangefinder lenses
(e.g. Leica, Canon, maybe Nikon) and normal focal length 35 mm lenses.
It will be a long time before any of these is nontrue, due to physical and
optical constraints (and even mount constraints).
SLRs are a real lens design challenge because space for the mirror means an
inverted telescope deisgn for lenses shorter than 80 mm (sort of a wide
angle lens way out front with a magnifier behind it to get the image to the
right size)--see problems with wide angles below).
Ultrafast telescopic lenses simply need HUGE elements (thus expensive: a
Nikon 200 f2 costs $1700)--doable but not marketable.
Fast wide angles cause you to run into problems with a conflict between
adequate diameter and high curature elements (you can't make a 3 inch lens
blank with a 1 inch radius of curvature).
Extremes in lens design always make trade-offs harder--large, high curvature
elements really strain efforts to control various aberations to give an
acceptibly sharp lens.
Finally, rising expectations for lens quality and rising film speeds for a
given sharpness since the days of the rangefinder have made that last half
stop extra speed just not worth the costs.
-- 
Darrel J. Van Buer, PhD
System Development Corp.
2500 Colorado Ave
Santa Monica, CA 90406
(213)820-4111 x5449
...{allegra,burdvax,cbosgd,hplabs,ihnp4,orstcs,sdcsvax,ucla-cs,akgua}
                                                            !sdcrdcf!darrelj
VANBUER@USC-ECL.ARPA