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Thread: Image circle too large?

  1. #61

    Join Date
    Sep 1998
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    GA
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    12,751

    Re: Image circle too large?

    Quote Originally Posted by Argentum View Post
    correct me if I'm wrong. Field of view (what is in front of the lens) is largely dictated by focal length. Angle of coverage(what is behind the lens) is largely dictated by lens design. The two are not necessarily similar angles.
    Depth of field is in front of the lens and is dependent on focal length, aperture, desired CoC.
    Depth of focus is behind the lens and is dependent on focal length.
    Angle of coverage is the cone of light thrown by the lens towards the film. It is dependent on the optical design of the lens and the focal length and aperture and magnification ratio.
    Angle of view is dependent on the format size of the film and the focal length of the lens.

  2. #62

    Join Date
    Dec 2001
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    NJ
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    7,570

    Re: Image circle too large?

    Quote Originally Posted by B.S.Kumar View Post
    I would think that a 38mm Biogon, or a 3" Pacific Optical are some of the lenses not included in most people's definition of "most lenses" I must confess to never having seen either!

    Kumar
    Kumar, the 3" PO is very closely related to the 75/4.5 Biogon as sold for Linhofs etc. The 38/4.5 Biogon was most commonly fitted to the Hasselblad Superwide and successors. I'm surprised you haven't seen one.

  3. #63

    Join Date
    May 2016
    Posts
    107

    Re: Image circle too large?

    Quote Originally Posted by Argentum View Post
    correct me if I'm wrong. Field of view (what is in front of the lens) is largely dictated by focal length. Angle of coverage(what is behind the lens) is largely dictated by lens design. The two are not necessarily similar angles.
    There are two ways of looking at field of view... One is the FOV that the lens projects, the other is the size of image area you use, only the second is focal length dependent.... Angle of coverage is the same as the first. What is in front of the lens is the whole angle that a lens can see, the angle of coverage is the same and is both in front or behind the lens... The lens doesn't know what size image area one uses, nor it "cares".

  4. #64

    Join Date
    May 2016
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    107

    Re: Image circle too large?

    Quote Originally Posted by Bob Salomon View Post
    Depth of field is in front of the lens and is dependent on focal length, aperture, desired CoC.
    ...and on mounting distance. There is no way (according to physics) that two lenses of the same focal length, projecting on the same size image area, stopped down to the same aperture and used for the same size print, to saw the same DOF if they are mounted in different distances from the image area...

  5. #65
    Moderator
    Join Date
    Jan 2001
    Posts
    7,298

    Re: Image circle too large?

    I'm going to close this thread.

    It was started by a LF beginner asking a straightforward question about flange focal distance, flavored with a bit of confusion about image circle that could also have been cleared up with a simple response. Instead, the poor OP has been drenched with a convoluted mess of irrelevant stuff that can't be anything but confusing.

    To mingliaozi: welcome to the Forum! Please do have a look at the various learning resources as recommended but also feel free to post additional questions here as you continue your LF explorations.

    Everyone else: no, we're not outlawing all forms of thread drift. But before posting, please take a moment and ask yourself whether what you intend to say really is appropriate and helpful in context. If you want to argue about third-order subtleties of applied optics, then please define a suitable topic and launch a thread for that purpose rather than hijacking a beginner's thread on an unrelated, very basic topic.
    Last edited by Oren Grad; 29-May-2016 at 20:51.

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