P3D Re: IMAX Window

["Peter Muyzers" <peter.muyzers@xxxxxxxxx>]

Marvin Jones wrote:
> They do, because 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."

In reality, making a stereo Imax movie isn't as simple as it seems at
first. Window violation is an undesired effect, but often inevitable when
trying to tell a story. Yes, Imax does have a large window, but sometimes
the window isn't large enough to avoid these window violations. 
A stereo Imax director tries to avoid panning and chooses rather for static
camera shots. When panning is absolutely needed, it has to be done slowly,
else there will be a lot of strobing (Imax only runs at 30 frames per
sec.).
Dollying in/out works great in Imax. This makes Imax perfect for e.g. ride
films.
(see message about P3D Re: The Next 3D Attraction?)
Now this panning technique leads to the "windowing" problem. If slow pans
introduce front objects into the window: Houston, we have a problem.
Thus the ideal way of introducing a front object is to have it emerge from
behind the screen. But everytime a front object has to be introduced in
this way, stereo Imax movies will become soon pretty boring.
So, bending the rules of "windowing" helps to make great stereo films.
Wether Imax is too much "in your face" or not, is a personal preference.
A general rule is to keep the film deviation for imax between 1/25 and 1/12
of the screen width. I can assure you: 1/12th will give you a headache.
Often, stereo is exagerated to have a difference between a boring "flat"
stereo film or an exciting stereo adventure.

Now everybody take a day off and go see some stereo Imax films. ;-)

Peter

--
Peter Muyzers
3D Animator / Digital Effects Artist
peter.muyzers@xxxxxxxxx

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