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10Re: [fulldome] more Full-Dome video thoughts

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

      I challenge such a comparison. Some of the best video star displays available
      today are the Digistars. I have sat in the domes that employ the latest and
      frankly remain unimpressed. One planetarium (the Astronaut Memorial
      Planetarium near Cape Canaveral) employed both a Digistar and a traditional
      Minolta projector in an attempt to have the best of both worlds. Not too many
      folks could afford to do that. If quality is the goal, as you imply, then
      high definition video will not be able to provide it.

      >
      > >
      > >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.

      Well if quality and substandard quality are the choices, I think the
      discussion is already over. If the stars provide a back drop for an
      astronomy-related program, then there is some things that could be done better
      with interlaced video than say with all sky panorama systems. Again, the
      sacrifice is resolution. You still cannot beat the resolution of still
      photographic film with video. Even high def. video can't do it. If motion is
      necessary, then the resolution may not be as important (but, the Adler does
      something like this now and I was not impressed with their rendition of it in
      their tilted dome).

      >
      > >
      > >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.

      You are still hedging. I have seen both. Had to in order to be part of the
      team that put together our system. Today, the quality is not there for video
      versus film. I doubt it will ever be. But, if that is all that is offered,
      then the public will never know the difference, much to their loss.

      There is a place for video. It is not in the replacement of the star field
      produced by electromechanical means.

      --
      J. Scott Miller, Program Coordinator Scott.Miller@...
      Gheens Science Hall and Rauch Planetarium
      http://www.louisville.edu/planetarium
      University of Louisville
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