[rollei_list] Re: Tell the tales of Triotars
- From: Jerry Lehrer <glehrer@xxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Sun, 05 May 2013 10:09:28 -0700
Richard,
I hate to quibble (he lied), but the fast Ektar lens for the Miniature
Speed Graphic was f3.7, not f3.8.
According to experts it was the same glass as the Medalist 100mm f3.5
AND the first Hasselblad
80mm f2.8. Different glass element spacing, but I find it hard to
reconcile that.
Jerry Lehrer
On 5/5/2013 9:41 AM, Richard Knoppow wrote:
----- 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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