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Thread: is there an easy to tell if a lens is a telephoto without any info or trying it?

  1. #1

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    is there an easy to tell if a lens is a telephoto without any info or trying it?

    In the last month I finally tried an Ilex 10 inch lens I've had for a year and discovered that it's a Telephoto that only uses less than 3 inches of Bellows draw.
    This caught me by surprise, since there was no info on the lens online, and from what I could tell no indication on the lens it's self.
    Although it's a Beautiful lens it won't work for what I want which is a display view camera at a gallery I will be featured at soon. I actually want children to play with my Calumet 4x5 view camera. Being able to focus it, and play with the movements.

    Then today I got a Komura 400mm f8 large format lens, and again discovered that it is a telephoto. This time I made the discovery online before trying it, and it turns out that it's amount of bellows draw is beautiful still allowing lots of movements.
    Oh, the price was right, free.

    This got me wondering if there is a way to tell if a lens is a Telephoto without trying it first?
    Plus is there a way to tell how much bellows draw it will use?

  2. #2
    IanG's Avatar
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    Re: is there an easy to tell if a lens is a telephoto without any info or trying it?

    Usually you can tel from the shape larger front elements smaller rear elements, it's a characteristic of LF telephoto lenses. Also if it's in a shutter the front part is much longer than the rear.

    Ian

  3. #3
    Jim Jones's Avatar
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    Re: is there an easy to tell if a lens is a telephoto without any info or trying it?

    If the size of the aperture appears to be the same when looking through both the front and the rear of the lens, it is neither telephoto or wide angle. If the aperture appears to be smaller when looking through the rear than when looking through the front, it is a telephoto. If vice versa, it is a wide angle.

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    Re: is there an easy to tell if a lens is a telephoto without any info or trying it?

    Just guessing here, but a 10" telephoto lens with a flange focal distance of less than 3" sounds a bit odd - like maybe a lens element is missing or turned around. Are you sure the lens is intact and complete? When you focus it - does the image come into focus evenly across the entire frame?

  5. #5

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    Re: is there an easy to tell if a lens is a telephoto without any info or trying it?

    Thank you for all the answers, Jim your method is so easy.

    Djdister, I sure agree with you. Although it appears to focus evenly and there are 1 or 2 similar looking lenses that I've found on line there is nothing that I would consider as a rear element. The image appeared beautiful in the gg, except it hardly covers 4x5, which also surprised me with a 10 inch lens.
    What I should do is take a photo with it and if the IQ is impressive keep it. Otherwise scrap it.

  6. #6

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    Re: is there an easy to tell if a lens is a telephoto without any info or trying it?

    Quote Originally Posted by Liquid Artist View Post
    Although it appears to focus evenly and there are 1 or 2 similar looking lenses that I've found on line there is nothing that I would consider as a rear element. The image appeared beautiful in the gg, except it hardly covers 4x5, which also surprised me with a 10 inch lens.
    Interesting. Is there any glass behind the diaphragm? That's the rear element.

    Telephoto lenses have less coverage than lenses of normal (non-telephoto, non-retrofocus) construction of the same focal length. For example, my 12"/4 TTH Telephoto barely covers 4x5.

  7. #7
    Tin Can's Avatar
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    Re: is there an easy to tell if a lens is a telephoto without any info or trying it?

    For your purpose which is a good one, I suggest the widest aperture as people need light to see, actual quality or sharpness on GG is way secondary.

    I have an old 4x5 set up with 8" f4.5 enlarging lens for the same purpose.

    8" so the bellows stretch a bit, looks cooler. Hope the bellows are red! Make sure what it is focused on is brightly lit.

    I saw a high end gallery with a Clyde Butcher show do the same thing, so passerby could peak from outside and see the upside down magic!
    where is the monolith

  8. #8

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    Re: is there an easy to tell if a lens is a telephoto without any info or trying it?

    I've run across a couple of sources which suggest that typical bellows draw for a telephoto lens would generally be about 60-66% of the focal length, so on a 10" lens that would be a draw of about 6 inches to focus. It might help to know exactly which model Ilex lens you have, or even a photo of the lens to compare...

  9. #9

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    Re: is there an easy to tell if a lens is a telephoto without any info or trying it?

    Quote Originally Posted by Liquid Artist View Post
    I actually want children to play with my Calumet 4x5 view camera. Being able to focus it, and play with the movements.
    I applaud your wanting to get kids interested in photography but you are more trusting than I would be. I would expect the lens to be covered with fingerprints and unknown sticky liquids, the bellows to be poked full of holes and the shutter to be jammed. I would not expect even a sturdy Calumet to survive.

    If I were doing this, I would simply put two sliding boxes together with a large magnifying glass on one end and a plastic ground glass on the other. If they destroyed it, no loss.

  10. #10

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    Re: is there an easy to tell if a lens is a telephoto without any info or trying it?

    Would not a simple way to test a long focal length for telephoto be to open the lens and shutter then aim the lens at the sun? The image of the sun could be focused on something as simple as your shirt or a wall.

    Measure the approximate distance from the aperture or lens flange to the image of the sun. If the measurement is in mm what the lens is marked for, then it is not a telephoto. If the measurement is considerably less than one could assume the lens was a telephoto.

    Am I far off on this thinking?

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