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Thread: Distortions Exposure and the ground glass

  1. #11

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    Re: Distortions Exposure and the ground glass

    Correct--as far as I know, the only thing that camera movements do is allow a change in perspective or focus plane. I don't see how a camera movement would make a straight line appear to be curved.

  2. #12

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    Re: Distortions Exposure and the ground glass

    We've been over this question of whether foreshortening is a form of distortion or not and whether camera movements can really change perspective or whether only changing the viewpoint can do that. The consensus was inconclusive at best.

    Still, when you turn a circle into an oval by positioning it at the edge of the frame, using a very near camera position and a short-focal-length lens, I consider the circle to be "distorted." Sure, it's not a lens defect, just a property of the projection. Seen from a purely geometric perspective (pun intended), any projection of a real-world 3-D scene onto a plane introduces distortion. I'm more than comfortable calling the elongation/foreshortening of image elements distortion, since it differs greatly from our expectation.

    Same with perspective: I'm happy with calling correcting converging verticals changing perspective. It sure changes the perspective point where the lines meet, which is a classic definition of the use of perspective in art. Of course, changing the size relationship of objects requires moving the camera.

    Best,

    Doremus

  3. #13
    ic-racer's Avatar
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    Re: Distortions Exposure and the ground glass

    Front standard movements do change perspective and object relationships, but I'd argue that front standard movements are "moving the camera around" because it changes the position of the lens in space. Important to note that the tripod does not necessarily "moves the camera around." You can move the tripod around and keep the lens in the same place, if you want. For example move tripod back and rack bellows out, etc.

  4. #14

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    Re: Distortions Exposure and the ground glass

    Quote Originally Posted by ic-racer View Post
    Front standard movements do change perspective and object relationships, but I'd argue that front standard movements are "moving the camera around" because it changes the position of the lens in space. Important to note that the tripod does not necessarily "moves the camera around." You can move the tripod around and keep the lens in the same place, if you want. For example move tripod back and rack bellows out, etc.
    Not if you have optical axis center tilts on the front. You do if you have base tilts.

  5. #15

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    Re: Distortions Exposure and the ground glass

    Perhaps it can be viewed this way:

    Regular camera movements seem to be pretty much like moving the camera in the x/y directions--up and down / left and right, and tilting back and forth. This changes the perspective and produces what people consider to be "distortion" in one way.

    Moving the camera forward and back from the subject also changes the perspective and produces what some people consider to be "distortion" or "foreshortening".

    So if your subject is the center of the sphere, regular movements allow the camera to move over the sphere surface and produce the sort of "fixed distance" distortion. But if you move in and out of the sphere, you get a "fixed latitude and longitude" but "variable distance" type of "distortion."

  6. #16

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    Re: Distortions Exposure and the ground glass

    Quote Originally Posted by Lou Baleur View Post
    Perhaps it can be viewed this way:

    Regular camera movements seem to be pretty much like moving the camera in the x/y directions--up and down / left and right, and tilting back and forth. This changes the perspective and produces what people consider to be "distortion" in one way.
    Are you sure? I ask because an inch of rise disappears a lot more foreground and brings a lot more steeple into the frame than simply moving the whole camera up an inch. Neither distorts anything.

  7. #17

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    Re: Distortions Exposure and the ground glass

    Quote Originally Posted by Dan Fromm View Post
    Are you sure? I ask because an inch of rise disappears a lot more foreground and brings a lot more steeple into the frame than simply moving the whole camera up an inch. Neither distorts anything.
    I think so--you're forgetting the tilt I mentioned. Rise is the same as a camera movement plus a camera tilt--then you correct the standards back to parallel to the subject plane--can you picture this?

  8. #18

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    Re: Distortions Exposure and the ground glass

    Lou, I know the difference between direct and indirect decentering movements. No matter what you say, decentering movements are not equivalent to moving the camera. They just sweep the cone of rays the lens projects across the film plane, keeping it perpendicular to the film plane.

  9. #19

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    Re: Distortions Exposure and the ground glass

    That's not exactly what I said. But I understand what you're saying. It's a communication thing, so let's just say I think we are in agreement and leave it at that.

    My main issue got derailed and I've now totally lost interest. I think this back and forth is mainly an issue over turf and who gets to speak with authority on certain subjects in this forum. Apparently, some people are allowed to know things (those in the old boys click) and some are not (the rest of us), and the rest must always "kiss the ring" or face the wrath of the click.

    I won't kiss any rings of any kind.

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