cwr%SCH-Gila@sri-unix.UUCP (04/07/84)
From: Craig W. Reynolds <cwr at SCH-Gila>
Date: 1 Apr 84 21:36:54-PST (Sun)
From: hplabs!tektronix!uw-beaver!cornell!vax135!floyd!clyde!watmath!wa
From: tcgl!dmmartindale @ Ucb-Vax
Subject: Re: high-speed film
... With 60 frames/sec, motion would be a lot smoother. Does it use
a single-blade shutter in the projector? That would get rid of the
double-image effects seen when something moves rapidly.
I think Showscan uses a single bladed shutter. The 60 hertz frame rate
does make the motion look better, higher sampling rates allows higher
frequencies in the motion with less noticable strobing. On the other
hand, higher frame rates do not make the problem (temporal aliasing) go
away, any more than using more pixels (higher resolution) on a display
screen makes the "jaggies" (spatial aliasing) go away. It merely
reduces the amplitude of the error.
BTW: the correct solution to the strobing problem is to use "long" (on
the order of a frame time) "time exposures" to allow the image to
integrate, to properly blur on the film. Unfortunatly for real cinema-
tographers, this means that the camera must do its close-shutter/pull-
down-film/open-shutter cycle in zero time (a mechanical impossibility).
And in fact, preferably the exposure periods of two sequential frames
would overlap to some extent (sort of a "cross dissolve") which -- since
the camera has only one frame behind the lens at a time -- is a logical
impossiblity.
Luckily, this is not a problem for people who make movies by computer
simulation...jerry@oliveb.UUCP (Jerry Aguirre) (04/23/84)
I agree with your point about strobing. The wagon wheels would just
spin backward at different speeds.
About your idea for zero interval or overlapped frames. Would it not
be possible to have two (or more) exposure paths. This would make it
possible to alternate exposure and film motion between the two paths.
With the right mechanism you could even overlap the exposures.
While getting the fine alignment between the frames would require a
precise mechanism this does not seem a great deal more difficult than
getting adjacent frames aligned in an ordinary camera.
As to the mechanism, I would imagine something like a rotating mirror
behind the lens that disolved the image from one frame to the next. It
would probably be necessary to have several frames between "adjacent"
images to allow the alternating film motion. This could be sorted out
when the negative in printed onto the positive so a standard projector
could still be used.
When it becomes cheaper to computer synthesize images than build sets
and costumes the problem will go away. Or will they deliberately
incorporate the strobing effect to simulate "real" film?
Jerry Aguirre
{hplabs|fortune|ios|tolerant|allegra|tymix}!oliveb!jerryRG.JMTURN%MIT-OZ@MIT-MC.ARPA (05/03/84)
The Emulsifilter process is done by Acme Animation (I kid you not. Does Wile E. Cayote buy from them?) I saw that demo as part of a SIGGRAPH demo reel (#7, and worth it for the Cranston-Csuri and III [Looker] sections.) Acme does traditional style animation with computers. They seem to do mostly Carrier Air Conditioning ads if you only watch the tape. Emulsifilter has been universally judged much inferior to normal film or video by everyone who has seen my copy of the tape. It looks something like you had put geletin on the lens and turned up the blue too high. One of my friends claims that the problem with video is that it looks too clear, so people who have been conditioned to film are distracted, but I feel the Acme process would probably be worse. James (JMTURN@MIT-MC.ARPA)