P3D Re: IMAX Window

[aifxtony@xxxxxxxxxxxxx (Tony Alderson)]

Marvin Jones (digest 3009) wrote:
>(...)they contend that because of IMAX's huge viewing area, it has no
>window. It was the source of an ongoing debate between David Starkman and
>Neil Archebaux (sp?). Neil argued that in IMAX, the screen represented
>infinity, while David argued that this placed many images much too far off
>the screen plane, making them difficult for some people to fuse. Obviously
>making the screen the "window" as is usual for stereo projection, and
>placing most of the action "behind" it would be taking it too far in the
>other direction, but David thinks (and I agree) that IMAX is a little too
>much "in your face."<

Before I start playing devil's advocate, I should mention that my tastes
are more in line with David's and Marvin's, but the late Noel
(Archambault--see your 3DCD) did have some good points.  I haven't been to
an IMAX show in over a year, but as I recall the seats are no closer than
10 meters to the screen.  Now, certainly we perceive stereo beyond this
distance, maybe out to 100 meters, but most of our stereo sense is in the
closer ranges.  I've seen on-screen parallax of 2 meters (or more!) in IMAX
movies, how much is pushing the image back 65mm (in parallax, not perceived
depth) going to matter here?  Some, not a lot.

The question of a stereo window in IMAX (LEEP made a similiar claim that
the extreme wide angle made the stereo window irrelevant, I tend to agree)
is somewhat different from the practice of converging the infinity points
at the screen instead of in the screen (at infinity!).  But this does
simplify a lot of the problems in projecting stereo movies, and in design
and construction of the cameras and projectors.  So there is a real
economic incentive for IMAX to work this way.  Trying to put infinity at
infinity in the theater could conceivably result in a worse
presentation...by introducing this complication you increase the chances of
screwing up.  And overall, IMAX has been a lot more successful, and
viewable, than just about any other system ever.  Sure, it could be better,
but I'm willing to cut 'em some slack.

Tony "Easy to Please" Alderson
aifxtony@xxxxxxxxxxxxx

http://www.directnet.com/~aifxtony/AIFX/home.html



------------------------------