>>IMAX doesn't run at a higher framerate, your probably thinking of
>>Showscan, which I believe uses a smaller flavor of 65mm (5 perf or 8
>>perf) or VistaVision (35mm film shot sideways and 8 perfs wide, double
>>the image area of regular 35mm motion picture film) at something like
>>60 frames per second. IMAX runs at 24 frames per second, but the
>>extreme size of each frame means a lot more space is taken up by less
>>frames, hence the time limit. The IMAX film Titanica was 90
>>minutes, but there was an intermission while they changed reels.
>
>You may be right, I don't remember - but I was pretty sure it ran at a
>higher rate, on different film. It may have been the same material,
>but the wheels are, what, two and a half feet across and four inches
>wide?

Well, it's 70mm wide, so whatever that translates to, I don't have a conversion table handy. :) I suppose they could make wider platters to take a bigger roll of film, but a 45 minute reel at 24fps weighs in at 200 pounds, and I imagine there is a weight limit for the platter system, and in what the projectionist may have to lug around at any given point.

They might have used a polyester based print stock instead of acetate or something like that for durability, given how long an IMAX feature can run in the same theater (and how expensive prints are to make). We had a few 35mm prints come in printed on that when I was a projectionist, and while they were a little lighter they were a pain in the ass because they built up static electricity really fast when it was dry out and, as we were warned, the film would break the metal bits of the projector head before breaking itself if there was a problem and it got jammed because the tensile strength of the stuff was so high. They were also thinner than normal film, and the difference between the trailers printed on the normal stuff and that was enough to throw it out of focus, so you had to ride it between the transition. (or I did, anyway...I know lots of megaplex projectionists don't give a shit--always pray for a film geek in the booth when you go to the movies :)

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"We are totally fluxed."
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Chad Collier
Digital Bitch
J. Random VFX Company