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7more Full-Dome video thoughts

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  • Don Davis
    Oct 2, 2000
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      J. Scott Miller wrote:

      >
      >So, what you are saying is that rather than reproduce a star field that shows
      >the subtle but vivid colors that stars show in the real sky, one should simply
      >settle for a mediocre star field, a star field where stars look like small
      >snowballs instead of points of light.

      I believe the best all dome video can be good enough to take the place of
      many of the traditional planetarium projectors, although the
      electro-mechanical star projectors with their decades of refinement
      obviously do one thing beautifully. High Def video is also capable of
      great subtlety as well as detail and colorful variety. I question depriving
      the audience of the chance of sitting at the center of the dome, where the
      view is least distorted, because of one specialized projector. Elevators
      also take up that ideal viewing position.

      >
      >But there are probably few audiences that want to feel like they are looking
      >forward when they have come to see the stars. A slight tilt is fine (ours
      >will be about 12 to 15 degrees) but I am glad we didn't opt for a dome tilt
      >more than that.

      Providing an eye level horizon line is important if a significant portion
      of the imagery attempts to reproduce an environment other than a starfield.
      At some point we are discussing preferences rather than quality or
      objective standards, and it's great we are living in a time where such
      choices are becoming increasingly available.


      >
      >Sorry, facts are facts. You don't get the resolution in video projection that
      >you get in film. You can kid yourself into believing it, but when all is said
      >and done, there is no comparison.

      Resolution is influenced by less obvious factors than the number of
      viewable line pairs on a piece of film. At the moment film is the
      unquestioned supreme acquisition medium for capturing real world moving
      scenery. I'm afraid that 70 mm film is necessary for this, which renders
      such footage all but impractical for people to obtain on demand. Once a
      sequence such as a time lapse is obtained it must be scanned (very
      expensive) and 'cleaned up' for high res video projection.

      I believe a filmed test subject scanned and shown on a well tuned multiple
      projection high def system would compare well with a 70mm film release
      print of the same subject projected with a fisheye lens. It would be
      interesting to see an actual comparison. Assuming the film camera has
      steady registration between frames, the video projection would be rock
      steady compared with whatever mechanical 'play' and focus variations a film
      projector might introduce. A 30 frame per second image has more 'temporal'
      resolution than film at 24 FPS, a fact that is especially noticeable when
      viewing dynamic subjects on a dome. In addition to visual performance
      issues the video image files would not gather scratches and other wear with
      each showing.

      Although importing wide angle real world moving images is still very
      difficult, computer generated images are where all dome video really takes
      off.

      Don Davis
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