[rollei_list] Re: Triotar
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Mon, 10 Oct 2005 13:48:50 -0700
----- Original Message -----
From: "Peter J Nebergall" <iusar4s@xxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Monday, October 10, 2005 8:53 AM
Subject: [rollei_list] Re: Triotar
I have the Triotar on an Ikoflex 1, and another (85mm f4)
on a short tele
for Contax. The Ikoflex is doubtful; the Contax lens
gives me excellent
work. Both are uncoated glass.
Peter Nebergall
Cooke Triplets are capable of very good performance but
are difficult to design because they have just enough
degrees of freedom to deal with all the basic aberrations.
Kingslake points out that if anything has to be changed the
entire design must be ammended. Triplets are also quite
sensitive to element spacing, Kingslake again points out
that this precision keeps triplets from being cheap to make.
The added surface of a Tessar gives the designer more to
work with especially in correcting higher order aberrations.
In practice a triplet must generally be stopped down more
than a Tessar or other more complex design and does not
cover as wide a field at a given stop.
Triplets vary all over the place in quality. Its
impossible to know which of many patented Zeiss designs was
used in the Rolleicord but Zeiss made some very good triplet
lenses. Triotar seems to have been used for a high quality,
fixed focus, lens, Novar for a front element focusing
triplet.
Triplets were used in the Rolleicord because it was an
"economy" model camera. It had a much simpler mechanism than
the Rolleiflex and used a less prestigious lens. When
Schneider began to produce high quality lenses at lower
prices than Zeiss after WW-2 the Xenar, a Tessar type of
excellent quality, began to be offered on the Rolleicord as
a deluxe version and slighly higher priced camera and on the
Rolleiflex as a slightly lower priced camera. Without
actually testing a number of Xenars and Tessars on an
optical bench its really not possible to compare them,
however, from reported experience they are very close in
performance. At the time Rollei began to offer the Xenar
Schneider lenses did not have the reputation of Zeiss, which
has had a somewhat mythical reputation over the years.
Probably, many thought it was a lower quality lens, which is
was not.
I have no idea of the quality of the Triotar used on
Rollei 35mm cameras. In general aberration scales with the
focal length so its possible, for example, to make quite
adequate f/2.8 Triplets for use on 8 and 16mm moveie cameras
but a similar lens would not be satisfactory on a 2-1/4 x
2-1/4 camera.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
---
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