A question for you physics majors...

Discussion in '35mm Cameras and Accessories' started by Steve Mack, Jul 20, 2010.

  1. Steve Mack

    Steve Mack Member

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    I currently own two micro (or macro) lens: a Macro-Takumar 50 f/4 and a Micro-Nikkor-P, 55 f/3.5. Both of these have small objective lenses, for a 50, and both are recessed so far into the mount that I really don't think I need a lens shade with either one, unless I point it direct AT the sun.

    So, here's my question: what demands are made on the optics for the micro/macro lens? I don't find this arrangement on any of my other 50s, and I'm sure there is a very good optical reason for the small, recessed lens (at least it looks small and recessed to me.) So, can anyone tell me what's up?:confused: I'm curious.

    Thanks to all who reply.

    With best regards.

    Steve
     
  2. ic-racer

    ic-racer Member

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    My take on it

    a) f4 = small diameter
    b) special 'long range' helicoid needs a longer barrel, thus setting the elements deep.
     
  3. frobozz

    frobozz Subscriber

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    I bet it also helps in the quest to get an extremely flat field for the resulting image.

    Duncan
     
  4. Ian Grant

    Ian Grant Subscriber

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    b - is correct because maceo lenses designed for bellows use aren't set back like this, but for focussing 1:1 etc you need a long helical.

    and . . . .

    a - is correct as well look how far set back an f2.8 50mm Tessar is, smaller diameter but also far smaller overall physical length of the optical cells.

    Also some macro lenses have built in correction to maintain a constant aperture as the focus closer.

    Ian
     
  5. mopar_guy

    mopar_guy Subscriber

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    For a regular "normal" lens, the distance from the lens to the subject is greater than the distance from the lens to the film. For any 1:1 Macro work, the distance from the subject to the lens is roughly the same as the distance from the lens to the film. For any magnification greater than 1:1, the distance from the lens to the subject is less than the distance from the lens to the film.

    For most Macro photography, due to the magnifications involved, a moving subject is not really a good thing and a slow lens is OK.

    The 2 Olympus OM 50mm Macro lenses are also built with small front elements that are deeply recessed and according to Olympus, no hood is required.
     
  6. narsuitus

    narsuitus Member

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    I really don’t think a lens shade will protect any lens from flare if you point the lens directly at the sun.