720pN – help please!

[Randall Raymond]

[Barry Green] “Transfer that 24fps to DVD and watch it on a progressive-scan DVD player connected to a progressive-scan TV and you’ll see exactly 24 frames per second, no repeating”

Right. That’s because of the incredibly quick refresh rate of plasmas and lcds dealing with digits and not lighting up phosphorus fast enough to keep it glowing.* But hooked up to a SDTV and the player pumps out a 30fps 60 field signal. It will still be 24fps to the eye.

‘The multiple-flashing repeat frames thing is a concession to the mechanical shutter of a film projector…’…and to save money on film – film cameras run at half the speed of projectors. Which was my point. Nothing is lost using 24pn – just the frames needed to accommodate 60i in certain cases – and those can always be added back in by the NLE. Going out to tape for example.

* I can remember as kid in the early fifties that our TV would flicker in certain lighting. The phosphors were not perfected yet. I think europe was ahead of us on that.

[Barry Green]

[Raymond Motion Pictures] ” film cameras run at half the speed of projectors”
But — they don’t. The projector feeds the film through at exactly the same speed as the film camera does. The projector displays 24 frames per second. It just flashes each frame twice (or three times) to even out light/dark flicker. It has nothing (nothing nothing nothing) to do with motion.

The projector cannot run faster than the film camera, or everything would be playing at double speed, of course.

Theatrical film projection is done at 24 frames per second. A film projector flashes the image multiple times only to even out the light/dark transition from when the shutter is closed. Using a bowtie/butterfly shutter lets them even out the open/closed timing moreso than using a half-moon shutter would, while still maintaining the same amount of overall shutter-open time.

[Randall Raymond]

[Barry Green] “But — they don’t. The projector feeds the film through at exactly the same speed as the film camera does. The projector displays 24 frames per second. It just flashes each frame twice (or three times) to even out light/dark flicker. It has nothing (nothing nothing nothing) to do with motion.”

You’re right. But it has everything to do with flickering. The camera cannot match the projector’s cadence – it would double expose each frame. The alternative would have been for the camera to shoot 48fps to reduce flicker in a matching projector. Instead, they chose 24fps to save film.

[Barry Green]

[Raymond Motion Pictures] “You’re right. But it has everything to do with flickering. The camera cannot match the projector’s cadence – it would double expose each frame. The alternative would have been for the camera to shoot 48fps to reduce flicker in a matching projector. Instead, they chose 24fps to save film.”

Sorry, I still don’t follow what you’re getting at.

There is no flicker whatsoever in a movie camera. Watch any movie transferred to video and you’ll see what I mean.

Flicker is solely the product of using a film projector. The projector technology was modified to project each frame twice or three times, in an attempt to minimize the flicker introduced by hiding the frame 50% of the time. But the nature of 24fps does not equal flicker, and projectors do not run the film faster than 24fps. It’s all 24 frames per second. Film projectors flicker because of their mechanical shutter, not because of the frame rate.