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Thread: Lens diopters for the complete idiot (me)

  1. #1
    Jac@stafford.net's Avatar
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    Lens diopters for the complete idiot (me)

    My situation - I built a low altitude aerial camera based upon a Zeiss 75mm lens. It is superlative with fixed focus at infinity. Very cool. Now I would like to bring its use to earth with just a few fixed focus distances.

    It is convenient that it accepts 138mm filters which are rather common in cine applications. Cine photographers are technically astute so I am thinking of getting one or two diopter lenses, or how many it requires to do some land-level images. (Sure there may be image compromises but I'm good with that in LF.)

    Sorry for so many words when my question is: what numerical diopter strengths do I need to bring this wide-angle 75mm to focus at specific distances such as 3', 15', 50' and so-forth?

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  2. #2

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    Re: Lens diopters for the complete idiot (me)

    Can't help with the diopeters, but that camera is a nice piece of work.
    Expert in non-working solutions.

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    Maris Rusis's Avatar
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    Re: Lens diopters for the complete idiot (me)

    Dioptres are just the reciprocal of the focal length expressed in metres. So a 1 dioptre lens added to a lens with a fixed infinity focus will get you focus at 1 metre, a 0.5 dioptre lens moves focus to 2 metres, 0.25 dioptre lens brings 4 metres into focus, and so on ....
    Photography:first utterance. Sir John Herschel, 14 March 1839 at the Royal Society. "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..".

  4. #4
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: Lens diopters for the complete idiot (me)

    Hyperfocal distance at f/16 is 62 feet, with focus from 31 feet to infinity.

    Do you need to focus closer?

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  5. #5
    ic-racer's Avatar
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    Re: Lens diopters for the complete idiot (me)

    Just a guess, that the large 'Cine' diopter lenses will cost more than the camera (link to tiny Bolex diopter that won't fit your camera for $450). If you do go that route, diopter math was made to be easy (addition and subtraction). Convert your 75mm lens to diopters (13 diopters)

    For very little money I'd make some graded focus shims, maybe different colors. Place between the lens mount and camera body.

    Do you have a ground-glass option? I don't have a 75mm that fully covers 4x5", but when I do use it, focus needs to be prefect otherwise the pictures are out of focus.

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  6. #6
    Mark Sawyer's Avatar
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    Re: Lens diopters for the complete idiot (me)

    We could go through the math of diopters being additive and your 75mm lens being a 13.333 diopter plus the +2 diopter added to give a 15.333 or 65.2mm lens but finding the focal distance gets into lens thicknesses and nodal points that move around when you add the diopter lens...

    Best to buy a cheap set of diopters and see what they do. Better yet, make a set of extension tubes...
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  7. #7
    Drew Bedo's Avatar
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    Re: Lens diopters for the complete idiot (me)

    Umm . . .The TravelWide accepts several 90mm lenses, is rigged with no bellows, and could be an aerial camera. It also has a focusing helical mount which allows for focusing at less than infinity.

    Its pretty cheap too.
    Drew Bedo
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  8. #8

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    Re: Lens diopters for the complete idiot (me)

    Drew, Jac's lens is a 75/4.5 Biogon. It is a gross heavy mostrosity probably not suitable for a Travelwide.

    The lens is quite usable on a conventional 4x5 monorail -- it was sold for that application -- but for some reason Jac doesn't want to do that. He's trying to modify a clever solution to one problem (aerial photography of distant subjects) for a rather more general problem (photography at closer distances). Could be that his starting point (that clever solution) is preventing him from seeing the obvious. Could also be that he wants a simple relatively compact fixed focus camera for near subjects.

    Putting shims between lens and camera body, as has already been suggested, seems the best way for Jac to get what he says he wants. I like the monorail solution better, but that's my preferences speaking, not his.

  9. #9
    Jac@stafford.net's Avatar
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    Re: Lens diopters for the complete idiot (me)

    Quote Originally Posted by Dan Fromm View Post
    Drew, Jac's lens is a 75/4.5 Biogon. It is a gross heavy mostrosity probably not suitable for a Travelwide.

    The lens is quite usable on a conventional 4x5 monorail
    I already have tripod-mountable cameras for 75mm (or 3" Pacific Optical (PO)).

    Click image for larger version. 

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    An interesting thing about this PO version is that the rear element is larger than the 4" dimension of the film plane. It covers 5x5"

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    And I have other builds, mostly strange.

    Thank you to all who answered my original question.
    Last edited by Jac@stafford.net; 21-Jan-2019 at 00:47.

  10. #10
    ic-racer's Avatar
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    Re: Lens diopters for the complete idiot (me)

    You have a couple of great cameras!

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