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Thread: That elusive term: "Perspective"

  1. #21
    Land-Scapegrace Heroique's Avatar
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    Re: That elusive term: "Perspective"

    Quote Originally Posted by Darin Boville View Post
    Most of the discussion here is like that--using the word "perspective" in different ways.
    --Darin
    Perhaps we’re divided into “broad-perspectivists” (who include line convergence in the term), and “strict-perspectivists” (who wouldn't).

    After the insights here, I'm in the former group – probably the minority one.

    Quote Originally Posted by aduncanson View Post
    I considered proposing that perspective is completely determined by the position of the lens (the front nodal point in particular) and depends on nothing else.
    A quick question for the technicians – does front axial swing (or tilt) change the position of the lens’ front nodal point?

  2. #22
    Mark Sawyer's Avatar
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    Re: That elusive term: "Perspective"

    Quote Originally Posted by Andrew O'Neill View Post
    viewpoint and perspective are the same...are they not?
    Not in the art and photography world.

    "Viewpoint" is simply the point from which a view is taken.

    "Perspective" is how an image space is technically organized within the frame. In art, perspective refers to the point-perspective system, foreshortening, etc. In the case of view cameras, we're generally talking about modifying the geometry of converging lines by changing the geometry of the camera system.

    (There are other types of perspective, like aerial perspective, the tendency of things to be hazier as they recede in the distance.)
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  3. #23
    Mark Sawyer's Avatar
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    Re: That elusive term: "Perspective"

    Quote Originally Posted by Heroique View Post
    A quick question for the technicians – does front axial swing (or tilt) change the position of the lens’ front nodal point?
    No, but a lens has two very interrelated nodal points, a front and a rear.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  4. #24
    Land-Scapegrace Heroique's Avatar
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    Re: That elusive term: "Perspective"

    Quote Originally Posted by Mark Sawyer View Post
    No, but a lens has two very interrelated nodal points, a front and a rear.
    If this is true (and one accepts aduncanson's proposal), then front axial swings (and tilts) appear to be Lens Movements that can not possibly change perspective by anyone's definition.

  5. #25

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    Re: That elusive term: "Perspective"

    Kodak's Photography with Large-Format Cameras (1977) has a chapter on Perspective. There it is quite clear that perspective involved the convergence, or lack of, of verticle and horizontal lines. Their Basic rules say to control perspective use the swing or tilt of the camera back.
    Cambo's download document on the 4x5 camera describes a change in perspective with a change in film plane.
    A series of collectable magazines called The Photo from Marshall-Cavendish in 1981 has a very good discusssion.
    It describes 4 perspective effects, convergence, diminishing size, foreshortening and texture gradient all as different forms of linear perspective.
    It makes the point that the only way to truely change perspective is to change the viewpoint.
    But from a given viewpoint, alterations of the appearance of perspective are made with the back.
    So to change the actual perspective, change the lens position.
    To change the appearance of perspective in the image, change the film plane.
    Regards
    Bill

  6. #26
    Mark Sawyer's Avatar
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    Re: That elusive term: "Perspective"

    Quote Originally Posted by Heroique View Post
    If this is true (and one accepts aduncanson's proposal), then front axial swings (and tilts) appear to be Lens Movements that can not possibly change perspective by anyone's definition.
    When the film plane is no longer latitudinally or longitudinally perpendicular to the optical axis of the lens, the geometric perspective is altered. It doesn't matter if the system goes off-axis front the front or the rear, although if you use the front swings and tilts, it may cause other changes, like softer resolution and fall-off or vignetting at the outer edge of coverage as the optical axis is no longer centered on the film. And that can be compensated for with shift and rise/fall.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  7. #27

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    Re: That elusive term: "Perspective"

    I am not sure that I support my proposition, but rather thought that it was worth discussing. I readily acknowledge that the way that the word perspective is usually used, it incorporates the effects of both viewpoint and convergence changes introduced by swings and tilts. I actually did wonder if folks more theoretically inclined than me (There are some here.) would make the fine distinction I described. By my reading of the responses, I would say that, no they do not.

    Like the rear nodal point, the front nodal point is, in general, located at some distance ahead of or behind the flange and so it can not be relied on to lie in the plane of the swing or tilt axis. When it does not, the front nodal point would move slightly with swings and tilts. Whether or not this is significant would depend on the type of photography you are doing. In general, it would only be noticeable if you were doing macro work or maybe in tabletop shooting.

    Now please somebody help me out of this realm of "How many angels can dance on the head of a pin?" I need help figuring out how to fix the crummy prints I made this weekend.

  8. #28
    Mark Sawyer's Avatar
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    Re: That elusive term: "Perspective"

    Quote Originally Posted by aduncanson View Post
    Now please somebody help me out of this realm of "How many angels can dance on the head of a pin?" I need help figuring out how to fix the crummy prints I made this weekend.
    I usually put mine face down in the tray of fixer for one minute with agitation, then a second tray of fixer the same way.

    Glad to help!
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  9. #29
    Land-Scapegrace Heroique's Avatar
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    Re: That elusive term: "Perspective"

    Thanks for the book recommendations and supportive clarifications above.

    As for the theoretical realm – heck, it’s refreshingly welcome for some photographers worn-out by field and mountain. It quickens one’s readiness to return with heightened awareness.

  10. #30
    おせわに なります! Andrew O'Neill's Avatar
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    Re: That elusive term: "Perspective"

    Not in the art and photography world.
    They're not?? Then I've been teaching art wrong all these years.

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