[Frameworks] more on projector speeds

[David Tetzlaff]

That graphic I was sending to Josh Guilford notes an interesting feature of the Pageant 250S, which relates to the whole discussion of how projection affects the 'look' of a film, not just the duration. 

Almost all projectors have a 3-blade shutter, so at 16fps they flicker 48 time-per-second, at 18 fps they flicker at 54 times-per-second, and at 24fps they flicker at 72 times-per-second. Now, I can definitely see 48 pulse projector flicker, and find it annoying (and I have trouble watching PAL TV, because I can see the 50Hz flicker and it bugs me). But those specs, 50Hz TV and 48 pulse film projection were set because MOST people supposedly cannot perceive flicker at those rates. I think it's safe to say, though, that 24fps/72 pulse flicker, and good old NTSC (59.97 field pulses/sec) look the same to pretty much everyone.

Anyway, not ALL projectors have 3 blades. Telecine projectors have five-blade shutters, with narrow openings at that (too dim to use for public projection). And some projectors have 2-blade shutters. The 250S has a "Kodak Super-40" shutter, which has spring-loaded movable blades. At the silent speed (18fps) the springs keep the blades in a three blade configuration, yielding 54 pulses per second. At 24fps though, the centrifugal force on the blades overcome the spring tension and the blades move into a two blade configuration, yielding "40 percent more screen illumination' and a 48 pulse flicker. However, depending on whether you change the speed before or after the projector is in forward motion, you can get the other shutter configuration with either sound or silent speed. That is, you can get 18fps in 2 blade mode (yielding 36 pulse flicker) or 24fps in 3 blade mode (yielding 72 pulse flicker).

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So if we really wanted to get anal retentive about how filmmakers intend their work to be shown, we'd have to know not just the frame rate, but the number of shutter blades. And the shutter-angle of however many opening there are...

And, really, 2fps one way or the other is one of the smaller variables between different instances of projection. Are the projectors in a booth so their mechanical noise is muffled, or out in the open where the projector noise is audible? How big is the image on screen relative to the audience-screen distance. How bright is the image? What's the color temperature of the lamp? 

(warning: irony ahead)

So if Warhol showed 'Sleep' with a 16mm projector running at 16fps, with a three 60-degree blade shutter, in an open room, 25 feet away from the screen, burning a 1000W incandescent lamp, through a 38mm f.1.8 lens, then that's the way to screen it, damnit. No messing with the flicker, no hiding the projector noise, no Xenon lamps that produce a cooler monochrome, or put out more light (unless you compensate the f-stop of lens to keep the lumens on screen constant, natch), no 25mm or 50mm lenses...  Anything else is ILLEGITIMATE!

Why, you might as well put Schwechater on a looper and run it in a museum gallery where people are walking in and out of the room all the time, and there's enough ambient light so they don't trip over each other, when we all know they should be in individual seats with side blinders locked in for the duration with one of those locking bars across their laps like a ride at Disney World! Show it RIGHT or don't show it at all!