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  1. #1

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    how long should be a bellow...

    How long should be a bellow on a 20x24 camera if I want to take portrait in a studio ?
    I know that it depend on the lens I will use and that I should have a bellow that is twice longer than the lens, so that I can use the 1:1 ratio...
    but what would you consider a good lens to make portrait on this kind of camera ?
    In fact at the biginning I will only use 16x20 sheet film in vertical position inside the 20x24 film holder that would be in horizontal position...

    Sorry if my english is not so good, I hope my questions are clear ?

    Thank you, T. Moenne-Loccoz.

  2. #2

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    Well, the normal focal length for 20x24 inches is approximately 800 mm. The normal focal length for 20x24 cm is around 300 mm. A portrait lens would be as much as twice as long as normal.

    There are very few 1600 mm lenses available, you might have to settle for a 1200, e.g., Apo-Ronar or Apo-Nikkor. There are more, but not many, choices at 600 mm.

    To get a better idea of your choices, see, e.g., http://www.cameraeccentric.com/html/info/goerz_3.html . Rodenstock and Nikon process lenses were made in a similar range of focal lengths and have similar coverages.

  3. #3

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    I have asked for a bellow 2,2 meter long, I think that it should be enough if I use a 42" lens. hope so !
    Thierry M.L.

  4. #4

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    Note that with ULF such as 20x24 inches, the scale of reproduction (inverse magnification) is going to be small. For example, if you are doing a head and shoulders shot with a field-of-view that equals 20x24 inches (not unreasonable), the magnification is x1 and the required bellows draw is 2x the focal length of the lens. With smaller formats, we only use bellows > 110% of focal length with "macro" shots, but "macro" is with reference to the film size and can be hit easily even at a measly 8x10 inches of film.

  5. #5
    Reinhold's Avatar
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    I did some testing with my new, soon to be released, 790mm f:5.4 meniscus lens.
    I wanted to verify the bellows draw needed to focus at 3 meters (10') and at 1.5 meters (5').
    When focused at infinity the bellows draw is 790mm, as expected.
    When focused at 3 meters, the bellows draw is 1000mm.
    When focused at 1.5 meters, the bellows draw is 1400mm.
    I converted a spare bedroom into a camera obscura for evaluating monster lenses.
    Unfortunatly, I can't evaluate the field of view with my set-up.
    Tim's post gives some insight on what to expect under similar conditions.
    Here's a data sheet on the new lens...

    Reinhold
    www.re-inventedphotoequip.com
    Attached Files

  6. #6

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    This meniscus lens could be an alternative, but if possible I would like to find a lens that would be a bit soft when wide open and pretty sharp when stopped down. In the 1000 - 1200 mm range what could be possible ? Of course if it could be mounted in a shutter it would be very nice. Perhaps I want too much ? Any idea of that dreamed lens that could cover 20x24 also at infinity ?

    Hope that what I said is correct ?

    Thank you for your answers. Thierry M.L.

  7. #7
    Dave Wooten's Avatar
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    Use a 450 mm lens and pull bellows to 800the mm, or the less
    [FONT="Arial Black"][/FONT]

  8. #8
    Dave Wooten's Avatar
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    ...pull to 800 mm or less
    [FONT="Arial Black"][/FONT]

  9. #9
    Dave Wooten's Avatar
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    At 1:1, the human head will fit in an 11 x 14 inch area on your film.
    [FONT="Arial Black"][/FONT]

  10. #10
    Dave Wooten's Avatar
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    You do not need an 800 mm lens or 1600 mm bellows to do 1:1 portrait on 20 x 24 film.
    [FONT="Arial Black"][/FONT]

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