[rollei_list] Re: Tell the tales of Triotars
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Sun, 5 May 2013 09:41:16 -0700
----- Original Message -----
From: "Sanders McNew" <sanders@xxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Sunday, May 05, 2013 12:26 AM
Subject: [rollei_list] Tell the tales of Triotars
Apart from the obvious difference in aperture, can anyone
speak to the differences (if any) between the f/3.8 and
f/4.5 Triotars? Does anyone think they can see any
discernible differences in how they render images? The
difference in speed seems slight -- why did F+H offer both
lenses? Is there any advantage to one over the other?
Sanders McNew
The answer may lie in the cost of the lenses. I
suspect the f/3.8 was offered because it was closer to the
f/3.5 lens on the Rolleiflex but the Flex originally came
with a slower lens. Another possibility is the size of the
shutter, the slower lens will fit a smaller shutter. Kodak
made the 127mm Ektar as an f/4.7 lens because the iris in
the shutter they used would not open wide enough for f/4.5
and did the same thing with an f/3.8 Ektar for press cameras
which is essentially the same as the f/3.5 lens in the
Medalist camera only slightly longer in focal length and in
a standard shutter.
Both Tessars and Triplets are best as slower lenses,
perhaps around f/6.3. At larger apertures they begin to lose
sharpness at the margins of the image. The f/3.5 and f/4.5
lenses are at their best for overall sharpness when stopped
down to around f/11.
You may know that the Triplet is the simplest lens that
can be corrected for all seven primary aberrations. They
were difficult lenses to design pre-computer because any
change in any parameter affects everything else. They also
are very sensitive to element spacing so require precision
mounting.
--
Richard Knoppow
Los Angeles
WB6KBL
dickburk@xxxxxxxxxxxxx
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