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From: recais@mhuxv.UUCP (CAIS)
Newsgroups: net.rec.photo
Subject: Re: f/1 lenses
Message-ID: <242@mhuxv.UUCP>
Date: Mon, 22-Apr-85 08:15:23 EST
Article-I.D.: mhuxv.242
Posted: Mon Apr 22 08:15:23 1985
Date-Received: Tue, 23-Apr-85 06:17:52 EST
References: <2720027@acf4.UUCP>
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 31

> Why is it that Leica has the only f/1 lens I've ever heard of?  And why
> don't they make it for their SLR line?
> 
> The best anyone else seems to be able to do is f/1.2.

Nikon also made a superspeed lens for their rangefinders
back in the late 50's. It was a 50mm f1.1 nine-element
design. Zunow had a similar lens (available in Leica
screw mount as well).
The Canon 50mm f0.95 made its debut with the Canon 7
rangefinder in the early 60's. It has seven elements.
These lenses were mainly for publicity and prestige
and aimed at the photo journalist. Canon always
upped the ante on competing Nikon RF lenses in an
attempt to be number one.
These lenses are not very practical. They are massive
and heavy, with residual abberations compounded by the
large aperture. The Canon lens has significant flare
and field curvature. The contemporary Leica 50mm f1 is
reported to vignette markedly. The use of aspheric
elements can help but the manufacturing cost does not
justify the extremely limited market.
I have used the Nikon f1.1 and would choose the f1.4
any time image quality is a consideration. The depth
of field of these high speed lenses wide open is
vanishingly small at close distances. In practical
terms flare reduces the working aperture (T-stop)
below the marked value. The bottom line seems to
be that cost, weight, and optical limitations do
not justify the extra half stop in speed over a f1.2.