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Thread: Lens question(s)

  1. #1
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    Lens question(s)

    This is probably a dumb question but I guess if you don't know and don't ask you stay dumb...

    Are the lenses for a 4 x 5 view camera the same as for an 8 x 10 view camera?

  2. #2

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    Re: Lens question(s)

    No, for the same coverage the 8x10 takes lenses of twice the focal length.
    A lens which is designed to be used on a 4x5 camera can't be used on an8x10, but an 8x10 lens can be used on a 4x5 camera.
    Wilhelm (Sarasota)

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    Re: Lens question(s)

    I've got some studying to do. That makes perfect sense though. Thank you

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    Re: Lens question(s)

    Think of 4x5 as "dx/crop sensor" for LF and 8x10 as "fx sensor"; you can use the smaller 4x5 film with lenses and/or cameras made for the bigger sizes like 8x10.

    Other than focal length and physical size, the lenses for the different formats are functionally similar.

  5. #5
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: Lens question(s)

    They can be, but the sizes are different.
    For example, a "normal" lens for 4x5 is about 150mm, while a "normal" lens for 8x10 is about 300mm.

    The main criterion is the diameter of the "image circle" (abbreviated IC below).
    The diagonal of 4x5 film is 163mm; that of 8x10 is 325mm.
    To fully cover the film, the diameter of the lens' IC must equal or exceed that diagonal.

    The IC can be found on the datasheet for a given modern lans. Vintage lenses may be a problem.
    For example, the IC of the Nikkor W 300/5.6 is 420mm. It can be used on either format.
    On an 8x10 it's a 'normal' lens, like a 50mm on a 35mm camera. On a 4x5 camera it's a long lens.

    The IC diameter also determines how much movement you can use for the lens on any camera.
    The larger the IC, the farther you can move the lens and still have full coverage.

    The other issue is the length of the bellows on the camera compared to the lens focal length.
    By definition, the distance from the lens "rear node" to the film when focused at infinity equals the focal length.

    Since the rear node can be located anywhere inside or outside of the lens, depending on the lens design, we use
    the "flange focal distance", which is measured from the front of the lensboard to the film. This is close to the
    optical focal length for many lenses, but may diverge for very short or very long lenses. Again, the datasheet
    will give you that value for any modern lens.

    In order to focus at very close distances (1:1 image), the lens must extend forward from its infinity focus by
    a distance equal to the optical focal length, not the flange focal distance. This is true for all lenses.
    Obviously, the camera bellows length limits the choice of lenses and the closest achievable focus.

    Just a quick overview. Hope it answers some of your questions.

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

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    Re: Lens question(s)

    Quote Originally Posted by jp498 View Post
    Think of 4x5 as "dx/crop sensor" for LF and 8x10 as "fx sensor"; you can use the smaller 4x5 film with lenses and/or cameras made for the bigger sizes like 8x10.

    Other than focal length and physical size, the lenses for the different formats are functionally similar.
    That makes sense. Thank you.

    Quote Originally Posted by Leigh View Post
    They can be, but the sizes are different.
    For example, a "normal" lens for 4x5 is about 150mm, while a "normal" lens for 8x10 is about 300mm.

    The main criterion is the diameter of the "image circle" (abbreviated IC below).
    The diagonal of 4x5 film is 163mm; that of 8x10 is 325mm.
    To fully cover the film, the diameter of the lens' IC must equal or exceed that diagonal.


    The IC can be found on the datasheet for a given modern lans. Vintage lenses may be a problem.
    For example, the IC of the Nikkor W 300/5.6 is 420mm. It can be used on either format.
    On an 8x10 it's a 'normal' lens, like a 50mm on a 35mm camera. On a 4x5 camera it's a long lens.

    The IC diameter also determines how much movement you can use for the lens on any camera.
    The larger the IC, the farther you can move the lens and still have full coverage.

    The other issue is the length of the bellows on the camera compared to the lens focal length.
    By definition, the distance from the lens "rear node" to the film when focused at infinity equals the focal length.

    Since the rear node can be located anywhere inside or outside of the lens, depending on the lens design, we use
    the "flange focal distance", which is measured from the front of the lensboard to the film. This is close to the
    optical focal length for many lenses, but may diverge for very short or very long lenses. Again, the datasheet
    will give you that value for any modern lens.

    In order to focus at very close distances (1:1 image), the lens must extend forward from its infinity focus by
    a distance equal to the optical focal length, not the flange focal distance. This is true for all lenses.
    Obviously, the camera bellows length limits the choice of lenses and the closest achievable focus.

    Just a quick overview. Hope it answers some of your questions.

    - Leigh
    Perfect. Not to be Captain Obvious here but is it wrong to say that the resolving power of LF film is orders of magnitude greater than that of a 35mm full frame sensor?

  7. #7
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: Lens question(s)

    Quote Originally Posted by Michael Lloyd View Post
    ...the resolving power of LF film is orders of magnitude greater than that of a 35mm full frame sensor?
    Absolutely true.

    If you scan a 35mm negative at 300dpi you get roughly 425 dots of information across the long dimension.

    Scanning an 8x10 negative at 300dpi gives you about 3000 dots of information across the long dimension.

    That's a seven-fold increase in resolving power if you're comparing identical film types in the two formats.

    (BTW... It's easier to answer positive questions "Is it right to say..." than to answer negative ones "Is it wrong to say...".)

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

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    Re: Lens question(s)

    Quote Originally Posted by Leigh View Post
    Absolutely true.

    If you scan a 35mm negative at 300dpi you get roughly 425 dots of information across the long dimension.

    Scanning an 8x10 negative at 300dpi gives you about 3000 dots of information across the long dimension.

    That's a seven-fold increase in resolving power if you're comparing identical film types in the two formats.

    (BTW... It's easier to answer positive questions "Is it right to say..." than to answer negative ones "Is it wrong to say...".)

    - Leigh
    Awesome. but how does it compare to a 22 megapixel full frame digital sensor?

    Positive vs Negative- I like that... I'm going to have to remember that. I program control systems for a living so for me ON and NOT OFF are just logic states. One of the hazards of working with Boolean logic every day is that the thought process for day to day life is often "If ((X and NOT Y) OR Z) Then X1=1 Y1=0, and Z=1 Else X1=0, Y1=0, Z1=0 EndIF" I think that carries over into my typing

  9. #9
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: Lens question(s)

    8 x 300 = 2400
    10 x 300 = 3000

    3000 * 2400 = 7.2Mp.

    If you scan at 600dpi, the result is 28.8Mp.
    If you scan at 1200dpi, the result is 115.2Mp.

    You can scan at higher resolutions if you wish.
    1200dpi is probably max for most good 8x10 films, but you might be able to do twice that.

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

  10. #10

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    Re: Lens question(s)

    Quote Originally Posted by Leigh View Post
    1200dpi is probably max for most good 8x10 films
    Other than massive file size, whats the downside to using the max resolution of an Epson v700 (ie 6400 dpi) or even 2400 dpi?

    Dan

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