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Re: Precision required for nodal point?

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  • Alan Ball
    ... [snip] ... The actual precision needed will depend on the angular field of view of your lens, how far you rotate the camera between adjacent shots, how
    Message 1 of 7 , Oct 1, 2007
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      --- In PanoToolsNG@yahoogroups.com, paul womack <pwomack@...> wrote:
      >
      > I am just setting out to make a wooden
      > pano head for my Canon a630.

      [snip]

      > But HOW precise do I need to be in
      > evaluating and building the nodal
      > point?
      >
      > 1/2 a mm?
      > 1 mm?
      > 5 mm?

      The actual precision needed will depend on the angular field of view
      of your lens, how far you rotate the camera between adjacent shots,
      how close to the no-parallax point the objects in the field of view
      approach, especially at the seams, and in general the amount of
      parallax mismatch you can tolerate in your panorama. For landscapes
      and even for most indoor shots, 5 mm would be accurate enough. For
      tabletop setups and the like where the subject approaches very close,
      you might need greater accuracy than that.

      Alan Ball
      scoundrel1728
    • Eric O'Brien
      This is entirely possible. I built a wooden panorama head a few years ago as a prototype, but never got around to the next step of refinement. Other than
      Message 2 of 7 , Oct 1, 2007
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        This is entirely possible.

        I built a wooden panorama head a few years ago as a "prototype," but
        never got around to the next step of refinement. Other than being
        rather larger and heavier than I'd like, it works fine! :)

        Since I thought I might be using different lenses or cameras (and
        because I expected that my "first cut" would not be perfect), I
        included fore and aft + left/right adjustment capability by including
        a couple of "Manfrotto 3273 Quick Release Adapter with 2372 Plate"s
        installed at right angles between the camera attachment point and the
        rotating base. The 3273/3272 pair seems to be priced about $45.00-
        50.00 (US).

        [And GOOD LUCK finding the product on the Impossibly Awful To Use
        Manfrotto site. Good Grief!!]

        If you don't mind re-creating your pano head several times ("OK, now
        drill the hole 1/64 inch *lower* this time"), then you don't need
        that stuff.

        Also, my camera is attached by way of a Quick Release Clamp, which
        allows some vertical adjustment.

        If you're using only a single camera and lens, you in theory could
        get away without using such things. You might have to make several
        versions before you decided that your positioning was good enough.


        A very useful tool in all this: a self-leveling Laser plumb/level
        thingy!

        It is easy to pay far too much for such a thing. Hunt around during
        the "holiday/Father's Day sales" times and see what you can find.
        Mine cost about $35.00 (US). The principle is astonishingly
        simple... A horizontal and/or vertical laser line is projected from
        an emitter that is DANGLING from an attachment inside the unit.
        Dangle means pendulum means... GRAVITY is running the show. What a
        deal... thank you Mr. Newton.


        ASSUMING that the little tiny laser emitter was correctly calibrated/
        oriented during manufacture, it will project a *very* accurate
        horizontal or vertical line. Get out your string-and-weight plumb
        bob or 6 foot (2 metre) construction level and challenge the results.

        What this is useful for: Adjusting or Confirming that the center of
        the lens is aligned with the vertical rotation axis (yaw) of the pano
        head. Similarly, that the center of the lens is aligned with the
        *horizontal* rotation axis (pitch) of the pano head.

        That is: you can project a laser line against your pano head, and
        pretty easily see how close the pivot points (holes) you've created
        match up with the center of the lens axis.

        Have Fun!!

        eo


        On Oct 1, 2007, at 2:10 AM, paul womack wrote:

        > I am just setting out to make a wooden
        > pano head for my Canon a630.
        >
        > Along these lines:
        >
        > http://www.worth1000.com/tutorial.asp?sid=161123
        >
        > I understand about the nodal point, and
        > needing to rotate about it.
        >
        > But HOW precise do I need to be in
        > evaluating and building the nodal
        > point?
        >
        > 1/2 a mm?
        > 1 mm?
        > 5 mm?
        >
        > BugBear
      • Erik Krause
        ... The wiki artikle (s.a.) is finished for the time being (diagram still missing). You should be able now to estimate what precision you need. Interesting
        Message 3 of 7 , Oct 2, 2007
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          On Monday, October 01, 2007 at 17:04, Erik Krause wrote:

          > > > As always: It depends. If you have structures in the near forground
          > > > it should be more precise than if you shoot in wide open places. For
          > > > general use I'd say 3mm precision is enough. However, if you use a fisheye
          > > > lens the no-parallax-point moves anyway: http://tinyurl.com/94g7c (scroll
          > > > down to Results and look at the Graph)
          > >
          > > My widest lens (wide end of zoom) is 41 mm
          >
          > And which angle do you intend to rotate between shots? Meanwhile I've
          > added the formula to http://wiki.panotools.org/Parallax
          > Some more info and a neat diagram (someone volunteer?) is still
          > missing, but may be it helps...

          The wiki artikle (s.a.) is finished for the time being (diagram still
          missing). You should be able now to estimate what precision you need.
          Interesting thing that the parallax error in the finished panorama
          does not depend (directly) on the used focal length (only on the
          rotation angle between shots and the displacement of the no-parallax
          point).

          Please tell me if there are some errors, since I did the calculation
          all on my own ;-)

          best regards
          --
          http://www.erik-krause.de
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