From: Richard Knoppow (dickburk@ix.netcom.com)
Date: 05/30/03-02:20:57 PM Z
----- Original Message -----
From: "Paul Repacholi" <prep@prep.synonet.com>
To: <curzon@tegenlicht.com>
Cc: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, May 30, 2003 12:04 PM
Subject: Re: please help for identifying a lens
> > The inscription on the lens says:
> > Rapid-Aplanoscop F:7,5.24x30
> > G.Rodenstock Munchen
>
> I'd post to the rec.photo groups, and see what the
Rodenstock site
> has on it. It seems you *may* have a lens that is worth
collecting.
>
> --
> Paul Repacholi 1 Crescent
Rd.,
> +61 (08) 9257-1001 Kalamunda.
> West
Australia 6076
Its a Rapid Rectilinear type lens. The numbers indicate
f/7.5 and a focal length of around 15 inches. The format is
in centimeters.
Rodenstock can probably date the lens from its serial
number. The USA distributor HP marketing (Bob Salomon) has a
serial number list but will date only via a phone call, not
e-mail, and won't post it.
The Rapid-Rectilinear is a symmetrical lens with two
cemented elements in each cell. The type was invented
simultaneously and independantly by Steinheil (as the
Aplanat) and Dallmeyer (as the Rapid Rectilinear) in 1866.
It quickly became the most commonly used lens. R-R type
lenses were made by practically all lens makers under a
great variety of names. They continued to be made up to the
early 1930's for use in inexpensive folding cameras. Bausch
& Lomb built millions of them for Kodak. I can't even guess
the date of this lens, the mounting probably would give some
clue.
The R-R is not an anastigmat, it was designed before the
high index low dispersion glass of Schott of Jena was
developed. Some backward curving field curvature is used to
average out the astigmatism. The lens must be used at fairly
small stops for the corners to be sharp.
Well designed R-R lenses can be quite sharp and quite
usable lenses. Both names refer to the lack of geometrical
distortion, a feature of symmetrical lenses.
R-R lenses were made as standard and wide angle types. The
coverage is partly a matter of the choice of glass. The
length of the barrel for a given focal length is a clue. The
longer the barrel the more limited the coverage but the
better the image.
I have no idea of the value of the lens as a collector's
item. At a guess, there were too many R-R lenses made for
the type to have any special value although very old lenses
may have value simply due to age. It is probably more
valuable as a usable lens.
--- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com
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