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#1
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Gundlach 5x7 Rapid Symmetrical W.A.
Hello:
I just picked up a Gundlach 5x7 Rapid Symmetrical W.A. lens, roughly 8" f.l. (don't have it in my hands yet). The Rapid/Symmetrical names sound like a Rapid Rectilinear type, then I read that Gundlach had an extra element modification to the RR to get around a patent, so is it possible it might be 6 element rather than 4? Then I read that some of the Gundlach lenses had disappointing centration. 6 vs 4 elements might make this worse? Finally, the seller said 'it ain't no Wide Angle'. From this vintage, did W.A. mean anything else, or was that a relative term that doesn't amount to wide angle these days? (Some older wide angles were really wide, so I'm confused). Is it a dog, worse than a dog, or a dog that only knows one trick? Thank you Murray |
#2
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Gundlach 5x7 Rapid Symmetrical W.A.
On 10/20/2007 5:54 PM murrayatuptowngallery spake thus:
[snip] Is it a dog, worse than a dog, or a dog that only knows one trick? Perhaps it's a lovable dog that needs a good home ... |
#3
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Gundlach 5x7 Rapid Symmetrical W.A.
"murrayatuptowngallery" wrote in message ups.com... Hello: I just picked up a Gundlach 5x7 Rapid Symmetrical W.A. lens, roughly 8" f.l. (don't have it in my hands yet). The Rapid/Symmetrical names sound like a Rapid Rectilinear type, then I read that Gundlach had an extra element modification to the RR to get around a patent, so is it possible it might be 6 element rather than 4? Then I read that some of the Gundlach lenses had disappointing centration. 6 vs 4 elements might make this worse? Finally, the seller said 'it ain't no Wide Angle'. From this vintage, did W.A. mean anything else, or was that a relative term that doesn't amount to wide angle these days? (Some older wide angles were really wide, so I'm confused). Is it a dog, worse than a dog, or a dog that only knows one trick? Thank you Murray What speed, certainly not f/1 :-) I can't find a Rapid Symmetrical W.A. but a Wide Angle Symmetrical is listed in a 1926 catalogue at f/16. No schematic is given but its described as a "wide angle rectilinear type" covering 85 degrees. The No.5 has a focal length of 8 inches and is specified for 8x10 plates. There were some wide angle rectilinear lenses made by others. The problem with the Rapid-Rectilinear type is that they are not corrected for astigmatism so must be stopped down for good sharpness away from the center. Astigmatism in a camera lens is a different aberration than astigmatism in the eye. In a camera lens it means that each point of light in the image has two points of focus where the point is focused as a line. At one point the line is axial, at the other it is tangential. In between these two locations the point is focused as a round blur spot. The less the astigmatism the sharper the point. Since the size of the blur is affected by depth of field astigmatism tends to be minimised as a lens is stopped down. The lack of correction of astigmatism comes from the lack of glass types with the necessary properties at the time the R-R lens was designed (1866). Until the development of Barium glasses by Schott ("Jena glass, about 1890), correcting a lens for both astigmatism and color was not possible. Ernst Gundlach was a curious character, Rudolf Kingslake has a short biography of him in his book on lens history (1) but also wrote a more lengthy bio of him (2). Gundlach designed several lenses where he added an extra element essentially go get around some existing patent. His version of the Rapid-Rectilinear, which he called the Rapid Rectigraphic, had three cemented elements in each half but two were essentially just one of the elements in the R-R split into two. The same with the Radar lens, essentially a Tessar with an added element which evidently does nothing. Probably Gundlach's most famous lens does not have his name on it. This is the famous, or notorious, Turner-Reich convertible. This is essentially a Zeiss Convertible Protar with the same sort of split element seen in the Rectigraphic and Radar. This lens was sold with all sorts of claims for its superiority but the reality is that its not up the Protar at all. The centering problems apply mostly to the T-R lens, which has 5 cemented elements in each cell. Lack of good centering will disturb the performance of any lens but I think the inherent performance of the T-R is not so wonderful to begin with. In general, the more cemented surfaces the more critical centering becomes. The method of centering cemented elements was changed sometime around perhaps the late 1940s but I can't be sure of the date. The original method was to center each lens on a centering machine and grind the edges as accurately as possible. The cementing was then done by clamping the edges. A later method is to center the lenses on the centering machine after cementing but before curing. After the entire assembly is cemented and cured the edges of the assembly are ground concentric and parallel. This results in more precise centering. The centering machine is essentially a highly accurate (with minimum run out) rotating tube on which the element to be centered is fastened with a gummy substance. A point of light is projected onto the lens and its image viewed in a small telescope. The lens is then moved around until both reflections (from front and back surfaces) are stationary and stationary with respect to each other. For general centering of elements the lens is then clamped by another tube from above and the edges carefully ground to be concentric and parallel. The same method can be used for getting two lenses exactly together except there are than four images to watch. I would like to know if your lens turns out to be something different. I have some access to older lens info so might be able to find out what it is if not the lens described above. 1, _A History of the Photographic Lens_ Rudolf Kingslake, (1989) San Diego, The Academic Press ISBN 0-12-408640-3 2, "Ernst Gundlach: Nineteenth Century Pioneer Optician" Rudlof Kingslake, _History of Photography_ 2, 361, (1978) -- --- Richard Knoppow Los Angeles, CA, USA |
#4
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Gundlach 5x7 Rapid Symmetrical W.A.
I couldn't tell from the photo what the scales say, so when I get it
I'll learn more. It has one scale that looked like shutter speeds, one that looked like maybe US stops and a third that said W.A. As far as being a dog, it's a rescue on at that...shutter is boogered up, iris missing or not working (wide open). It's an opportunity, not a problem. I get to actually make Waterhouse stops instead of just recommending them to others! Hopefully it has some interesting quality, and is really as wide as predicted. All my other RR's are Kodak 3A type, not fast, not wide. I'll let you know, Richard. Thanks, both. |
#5
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Gundlach 5x7 Rapid Symmetrical W.A.
"murrayatuptowngallery" wrote in message ups.com... I couldn't tell from the photo what the scales say, so when I get it I'll learn more. It has one scale that looked like shutter speeds, one that looked like maybe US stops and a third that said W.A. As far as being a dog, it's a rescue on at that...shutter is boogered up, iris missing or not working (wide open). It's an opportunity, not a problem. I get to actually make Waterhouse stops instead of just recommending them to others! Hopefully it has some interesting quality, and is really as wide as predicted. All my other RR's are Kodak 3A type, not fast, not wide. I'll let you know, Richard. Thanks, both. Let me know what kind of shutter its in if you can tell. That will also give a clue as to the age of the lens. For some reason both Bausch & Lomb and Kodak continued to mark Rapid Rectilinear lenses with US stops long after the system went out of use. B&L built most of the Kodak R-R lenses up to the early 1930's. -- --- Richard Knoppow Los Angeles, CA, USA |
#6
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Gundlach 5x7 Rapid Symmetrical W.A.
It arrived today.
I learned it has a Waterhouse slot, 2 air cylinders and springs that look as modern as any (I guess I never really thought about helical tension springs looking the same). Number (serial?) on the back, nothing identifying the shutter it yet. f/stop scale marked 6.2 - 45, so it must be newer than US stop style..but Waterhouse stops certainly SEEM older than 'real' f- numbers. The scale about the f-stop scale must tell something about the Waterhouse stop required, otherwise I don't see a point to labeling the lens body if the Waterhouse stops are individually marked and spend more time external to the lens than part of it. I'm easily impressed - little lenses that throw large images. |
#7
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Gundlach 5x7 Rapid Symmetrical W.A.
"murrayatuptowngallery" wrote in message oups.com... It arrived today. I learned it has a Waterhouse slot, 2 air cylinders and springs that look as modern as any (I guess I never really thought about helical tension springs looking the same). Number (serial?) on the back, nothing identifying the shutter it yet. f/stop scale marked 6.2 - 45, so it must be newer than US stop style..but Waterhouse stops certainly SEEM older than 'real' f- numbers. The scale about the f-stop scale must tell something about the Waterhouse stop required, otherwise I don't see a point to labeling the lens body if the Waterhouse stops are individually marked and spend more time external to the lens than part of it. I'm easily impressed - little lenses that throw large images. The shutter could be any of several. One of the cylinders is the speed regulator, the other to trip the shutter with an air hose. It should have a hose fitting on the bottom. If it has a stop scale it must once have had an iris diaphragm. A slot may have been cut later for Waterhouse stops. About the only lenses I know which have both an iris and a slot are process lenses where the slot was used for special stops for process work or for filters. If this is a standard make shutter it may be possible to fit the cells into a newer shutter made by the same company. US stops are calibrated in terms of relative exposure time but are otherwise arbitrary. US-16 is the same as f/16 so US-8 equals f/11, US-4 equals f/8, etc. The stop scale could be for either system but, assuming the lens is some variation of the R-R lens its likely to be US stops. -- --- Richard Knoppow Los Angeles, CA, USA |
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