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I am pretty sure that Sony Lincoln Square (NYC) is 48fps-capable.

I mentioned the 12k because the Detroit Science Center just re-opened with a new 15k lamphouse that almost doesn't fit in their doghouse. I forgot about the 4k and had absolutely no idea there was a 7k classic!

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"Momentum" was the 48fps IMAX film at EXPO 92 in Seville.
CLICK HERE

The NFB and Giant-Screen Filmmaking http://www.nfb.ca/E/4/2/imax.html

The above image is an animated gif, so Joe needs to turn on his animations.

As the film enters the projector at the input sprocket, a burst of air "encourages" the film to form a loop in the rotor gap. The gap is actually a "pocket" in the rotor, so that it also acts as a shutter.

As the loop approaches the aperture block, it increases in size to 15 perfs (1 frame).

As it reaches the aperture block, the cam pins retract and return, "catching" the tail of the loop and decelerating the film. This aligns the perfs with the registration pins as the loop rolls across the face of the field lens, where it is sucked into place against the registration pins and projected.

A flicker shutter passes across the light field and the same frame is projected again (the same effect as the bow-tie shutter in a 35mm projector).

After the next frame is rolled across the field lens, the loop gradually diminishes in size as it exits the projector via the output sprocket.

The film is not moved in an intermittent movement, but is looped and rolled by the rotor through the projector. Imax calls this a "rolling loop". Iwerks calls this a "lateral loop" because it is a horizontally moving loop (and Imax used "rolling loop" first).

Incredibly over-simplified, but there it is.

For GT-3D, take two rotors, stack them on top of each other, and lock them together with a 11.25-degree offset. The right eye projects while the flicker shutter passes the left eye.

For SR-3D, take two projectors and interlock them with a PLC.

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Gord: Now that makes more sense than what I was seeing. I was seeing the cam pins as a "holdback" so the loop could enlarge, but now I can see it catching the tail of the loop to allow the film to align with the registration pins on the aperture block. If I pull back the stator and turn the rotor by hand, I see the registration pins are holding back rather than the cam pins.

Contrary to the previous mis-information, Iwerks has both 24 and 48 fps projectors and refers to it's 1570 projector as a "rolling loop" projector, which it is. Iwerks also has several 870 and 1570 cameras in both 2D and 3D configurations as well as underwater housings, helicopter mounts, etc.

The linear speed of the 15 perf, 70mm film at 24fps is 337.5 feet per minute and 675 ft/min at 48fps (Like at Disney's Soarin'). That's about 3.8 and 7.6 miles per hour.

Think about it.... the projector is stopping and projecting and accelerating the film at those rates while projecting a rock-solid image without damage to the film!

A typical 24fps, 40 minute 1570 print is 2.5 miles long and costs about $20,000.

A standard 35mm feature runs about 1.0 mph and the print costs about $1500-$2000.

YIKES!!!!!

>>> Phil

Brad, is it possible to put Adam's illustration and explanation available for download in "manuals" or "pictures" along with a representative full size three frame segment of the film itself and image of the head?

Jerry, one frame is exactly the size of the shuttered rotor gap. The edges of the shutters on the gap match the frame lines. The loop is not a full frame in size until it rolls onto the field lens and then it immediately begins to reduce as it registers and exits the field lens.

As the film passes the input sprocket and enters between the rotor gap and the input stator (the guide on the non-rotor side of the film), a jet of air pushes the film against the stator while the input sprocket feeds film into the loop. (This causes a loop form into the rotor gap rather than a wad of film at nearly 6 feet per second. [There is a reason why we call them film "crashes"]) The air lasts just long enough for the loop to take shape, then the loop enlarges without any further assistance (other than being fed by the input sprocket) as it travels along the rotor.

Also, I have slowed down the animation on the graphic above. You may have to refresh.

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With a service contract, I would say that if there is anything endangering the print or significantly hindering the presentation, don't run the show. Without a service contract, I guess it depends on how much money your boss wants to spend/lose.

In the 35mm world, I've had projectors temporarily held together with duct tape, baling wire and vice grips to keep the show on the screen. And I think just about everyone's spun a platter or two by hand for an hour to make it to the end of a show.

Look above or look below. Either way, make sure you refresh.

Also, keep in mind that the rotor is moving just one frame per gap. On a GT, there are 5 or 6 frames between the input sprocket and the aperture block, depending on how you count it. I think it's the same on an SR, but it's been a while.