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#31
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BC writes: I suspect that the original definition is the one
involving the telephoto ratio that optics people have always used, and the other definition grew up around a popular misunderstanding of the term. I agree. In the 'old days' a thin pocketable rigid camera was not in vogue as it is with today's very thin digital. Foldable cameras were the compact camera of yesteryear, and rollfilm or 35mm canister thickness forced cameras to all have a certain minimum for the body depth. And cameras with telescoping lens assemblies that nested into the body for storage were possible even without telephoto design being needed. And telephoto design lenses were not very terrific optically until the science of lens design was greatly improved. So telephoto design lenses (vs. long focus lenses) were used primarily for long focal length only to keep lens length (and weight) down, but the design was not needed for 'normal' focal length to keep the front-element-fo-film distance small in order to permit a thin camera body. --Wilt |
#32
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BC wrote:
I suspect that the original definition is the one involving the telephoto ratio that optics people have always used, and the other definition grew up around a popular misunderstanding of the term. I recognize that usage rules, but reserve the right to complain about it! The technical meaning made a lot of sense to large format camera users. If you want a 15 inch (380mm) lens on your 4x5 Graflex, you definitely want a telephoto lens, because you don't have enough bellows extension to cope with a regular lens that long. It made a lot less sense to the users of miniature cameras. The 135 mm lenses for the Leica (Elmar and Hektor) were a little longer than 135mm from the film plane to the front surface of the lens, but they filled much the same function as the 15 inch lens on the Graflex. The 135mm Sonnar lens for the Contax was only around 129mm from film plane to the front of the lens when focussed at infinity and thus was a telephoto by your definition. I don't think that making the lens slightly shorter was an important factor in the design: it was just how Bertele's design worked out. It seems a little odd to call the 35mm lens on the Olympus Stylus Epic a telephoto lens, and to deny that status to a 300mm Nikkor. People who study photographic optics, large-format camera users, and language pedants will all know what is meant, but the much larger group who know only the popular meaning will not be able to make any sense of it. Technical vocabulary often acquires popular meanings which are only slightly connected to their technical meanings. Even good dictionaries sometimes list the popular meaning and miss the technical one. For instance, "milled coinage" has a technical meaning of "coins struck with a machine, originally a screw press, later a steam driven or electrical press" and has nothing to do with reeded edges except that milled coins often have such edges. But in popular language, and even in some dictionaries, it does refer to the edges and one can be accused of being pedantic if one insists on the technical meaning. Peter. -- |
#33
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"BC" wrote in message
oups.com... I suspect that the original definition is the one involving the telephoto ratio that optics people have always used, and the other definition grew up around a popular misunderstanding of the term. The later should be 'telescopic', as in collapsible. No? My two-bits worth. |
#34
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jjs wrote: "BC" wrote in message oups.com... I suspect that the original definition is the one involving the telephoto ratio that optics people have always used, and the other definition grew up around a popular misunderstanding of the term. The later should be 'telescopic', as in collapsible. No? My two-bits worth. Then should a "telescope" be collapsible or only if it is a "telescopic telescope"? |
#35
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wilt wrote: BC writes: I suspect that the original definition is the one involving the telephoto ratio that optics people have always used, and the other definition grew up around a popular misunderstanding of the term. I agree. In the 'old days' a thin pocketable rigid camera was not in vogue as it is with today's very thin digital. Foldable cameras were the compact camera of yesteryear, and rollfilm or 35mm canister thickness forced cameras to all have a certain minimum for the body depth. And cameras with telescoping lens assemblies that nested into the body for storage were possible even without telephoto design being needed. And telephoto design lenses were not very terrific optically until the science of lens design was greatly improved. So telephoto design lenses (vs. long focus lenses) were used primarily for long focal length only to keep lens length (and weight) down, but the design was not needed for 'normal' focal length to keep the front-element-fo-film distance small in order to permit a thin camera body. --Wilt The first wide-angle telephoto lenses were introduced by Olympus back in the mid-1970's when they began marketing extremely compact 35mm film cameras. The first patent reference that I'm aware of is U.S. 3,951,523 (assigned to Olympus), which features lens designs covering 62 degrees field of view (suitable for a 35mm focal length on 35mm film format) with a telephoto ratio less than 0.9. This lens type became extremely popular during the late 1970's through the 1980's, but began to decline during the 1990's when compact zoom lenses started to become much more common. The use of a true telephoto construction proved beneficial even for a slightly wide angle lens because camera thickness is a critical parameter. If a camera is too fat, then you can't put it in a shirt pocket. Even though you are correct that the film canister represents an irreducible minimum for the camera thickness, you still need a very compact lens system to ensure that the actual thickness doesn't get too much larger than the absolute minimum value. You're also correct that telescoping lenses help reduce thickness. However, this construction was used almost entirely with zoom lenses, so fixed focal length compact 35mm cameras have always required a compact lens design. True telephoto lenses are almost never used on compact digicams. These cameras achieve compactness mainly by the use of a small image format, and to a lesser extent by clever packaging (e.g. folded optical path). Brian www.caldwellphotographic.com |
#36
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jjs wrote:
"BC" wrote in message oups.com... I suspect that the original definition is the one involving the telephoto ratio that optics people have always used, and the other definition grew up around a popular misunderstanding of the term. The later should be 'telescopic', as in collapsible. No? My two-bits worth. 'Telescope' means far-watching. Funny how it has become associated with things like a collapsible fishing rod... http://www.bartleby.com/61/roots/IE488.html -- Lassi |
#37
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"Lassi Hippeläinen" wrote in message
... 'Telescope' means far-watching. Funny how it has become associated with things like a collapsible fishing rod... http://www.bartleby.com/61/roots/IE488.html Metathesized this! (extended grin) |
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