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Thread: Lens with 4-5 foot Image circle?

  1. #1

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    Lens with 4-5 foot Image circle?

    Hey friends,
    I'm looking to do some camera obscura work. The focal length is something around 5 feet and the image circle diameter needs to be 4-5 feet. Does anyone have experience with lenses that can do this? Will it have to be a completely custom job or are there lenses I can buy for this?

  2. #2

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    Re: Lens with 4-5 foot Image circle?

    Are you shooting landscapes or nearly life-size portraits?

    If landscapes, you'll have to adjust your expectations downwards. Focal length = image circle ==> lens covers around 53 degrees at infinity. The only findable sixty inch lenses for larger formats are all process lenses. There are none as long as you want with as much coverage as you want.

    If nearly life-size portraits then the image circle at infinity has to be only 2 - 2.5 feet. Most 800 mm and longer process lenses will do this.

    Why do you need a five foot lens?

  3. #3

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    Re: Lens with 4-5 foot Image circle?

    Because that's the size of the room, I bet.

  4. #4

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    Re: Lens with 4-5 foot Image circle?

    Garrett, that evil thought crossed my mind, along with the even more evil though that if that's what the OP is making it will be useful only for landscape work. And we know that the lenses needed for landscape work don't exist.

    The alternative, near-life size portraits, will need roughly a ten foot room if the OP uses a five foot lens. Which opens the possibility that the OP has a bit to learn. Or, perhaps, that I missed something important.

  5. #5
    おせわに なります! Andrew O'Neill's Avatar
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    Re: Lens with 4-5 foot Image circle?

    Pinhole.

  6. #6
    Tin Can's Avatar
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    Re: Lens with 4-5 foot Image circle?

    sin eater

  7. #7

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    Re: Lens with 4-5 foot Image circle?

    http://www.abelardomorell.net/posts/...al-geographic/

    Simplest is a pinhole (about the size of a coin for room-sized camera obscura)

    If you can find a lens the right focal length it will decrease the exposure times, but most rooms require lenses a few metres in focal length, and they are not commonly available, even if you look at standard tinkerer's supplies like eyeglasses blanks, or the front elements off cheap telescopes and binoculars. There is also the problem of focussing.

    A converging singlet with a diverging one behind it will allow you to adjust the focal length by moving them further apart or closer together. The problem will be getting hyper wide angle coverage if you want to have images on the side walls.

    Morell has used a simple lens and a prism for his most recent colour work, where the image is right-way-up. Most of these images are more planar views of the back wall than the more 3D views he used to take in B+W with pinhole.

    A final option is to take two wide angle lenses and mount them back to back with enough space between them that the rear lens re-projects the image formed by the front one. Manual lenses for film-era 35 mm, or cheapie zooms for DSLRs are common enough, so angles up to 24 mm equivalent are fairly simple, but getting really wide coverage to fill up the side walls is hard and/or expensive.

    With all of these, blocking out all other light is at least as important as which lens you use or how well it is focussed.

  8. #8
    JoeV's Avatar
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    Re: Lens with 4-5 foot Image circle?

    Try an L3177 from Surplus Shed. 42.4mm diameter, 4000mm focal length (that's about 13 feet), coated positive meniscus lens. $4 per single unit.

    ~Joe
    The photograph and the thing being photographed are not the same thing.

  9. #9

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    Re: Lens with 4-5 foot Image circle?

    Regarding professional lenses covering more than one meter in image circle, you may have a look at this compilation maintained by Henri Gaud on the French MF+LF forum. Go directly to the end of the list, you'll find a 1800 mm (~= 6 feet) Apo Ronar covering 1300 mm in diameter according to the official data sheet (about 4 feet), but with very high specifications in terms of distorsion and sharpness. Weight : 8 kg = 19 Lbs.

    http://www.galerie-photo.info/forumg...?3,27153,27153

    To the best of my knowledge, one of the actual uses of those huge repro lenses with a field above one square meter, in the good old days, was analogue photogravure for large size road maps.

  10. #10

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    Re: Lens with 4-5 foot Image circle?

    Henri's admirable lists are comprehensive but are riddled with errors. This link http://1drv.ms/1w0vbMD contains a list of links to lens catalogs and useful compilations of lens data. One of these days I'll add data from CEDIS-Boyer fiches techniques.

    Of particular interest to people who want long lenses with reasonable coverage:

    http://www.galerie-photo.com/apo-process-nikkors-en.htm All of Nikon's process lenses.

    http://1drv.ms/12OFqc2 All of Rodenstock's process lenses.

    As far as I know there's no good source for Taylor, Taylor & Hobson (sometimes badged Cooke) or Wray process lenses. For them, buy a copy of A Lens Collector's Vade Mecum and look 'em up. Buy it from http://www.antiquecameras.net/

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