Auteur: Dan Fromm
Date: 29-08-2004 19:07
Carlos, teleconverters serve several purposes. For some people, having a TC is a way of avoiding owning or carrying a long lens. Instead of getting, say, a 400 mm lens, one gets a TC to use on the 200 mm one already has. TCs can also be used to gain magnification, as in closeup photography, but for people who shot 24x36 or roll film SLRs, I think the most important reasons to own and use a TC are economic.
What you've been told already about extension tubes was correct and well-written but perhaps incomplete. People who don't own macro lenses for 24x36 are attracted to extension tubes for economic reasons. Most 50 or 100 mm lenses for that format perform better in the range their mounts will allow than at shorter distances, but extension tubes can cost less than a macro lens. And carrying, e.g., a 50/1.4 and a 50/3.5 at the same time is absurd.
That said, many macro lenses for 24x36, for example my 55 and 105 manual focus MicroNikkors, are designed to be used on tubes at magnifications between 1:1 and 1:2. This allows the maker to use a shorter and, presumably, less expensive focusing helical. Compare this with Steinheil's former macro lenses in Exakta and M-42 mounts. My old 135/2.8 Auto-Tele-Macro-Quinar had a pair of nested helicals; it must have cost a fortune to make.
As for using extension tubes on large format, I plead somewhat guilty. I shoot a 100/6.3 Reichert Neupolar on my 2x3 Graphics. The lens is held in front of a #1 shutter by an adapter. Graphics have very short bellows so I find it useful to insert as much as 60 mm of M39 extension tubes between shutter and lens to get more magnification. With more extension, the shutter will vignette. A special case, some would say pathological, but for me a good way to get the magnification I want without using a shorter lens.
Best regards,
Dan
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