Re: how much of what we see is black?

From: db (email suppressed)
Date: Wed Oct 31 2007 - 15:16:38 PDT

On Oct 31, 2007, at 11:10 AM, Flick Harrison wrote:

> You can move your head around while watching a movie, they seem to
> argue (though they are using the bicycle-spoke example rather than
> cinema itself), and the movie still seems to be continuous, rather
> than becoming jerky and blocky as the sequential after-images fail
> to line up. Therefore no afterimages exist.
> But this obviously assumes you are moving your head around fast
> enough to cause a significant difference - more difference than,
> say, an object moving quickly across a giant cinema screen image -
> within 1/48th of a second. Heads don't move that fast. And if
> they did, it would no doubt alter the perception of the image,
> assuming the info from your inner-ear fluid wouldn't clear up the
> confusion.

for a moment of "lightness" along the lines Flick is addressing above:

Dear Cecil:

Recently you put down an anonymous writer who asked, "How come when
you hold a chopstick in your teeth and pluck it, the TV screen
shimmies? Nothing else shimmies." You ascribed the effect to heavy
metal poisoning. Well, Cece, I think you dismissed the question
prematurely, without trying it. This effect does occur and results
from a vibration of the eyes (connected to the tooth bone) at a
frequency near that of the vertical scan rate on the TV, producing a
visible modulation effect of shimmying, speaking vernacularly. The
other objects in the visual field may appear slightly fuzzy, but they
don't shimmer. Chopsticks are fine, but if you want to see the effect
more clearly, vibrate your jaw or head with an electric vibrator
using different speeds while viewing TV. Hope this shakes you. Find
that letter and apologize. --Jim S., Dallas

Dear Jim:

I can't stand it. Every time I rummage through the circular file
looking for a letter exemplifying the depths to which the Teeming
Millions have sunk--believe me, you'd feel the same impulse if you
had this job--I come up with somebody who's tapped into some lost
truth of physics. As a matter of fact, I did try this silly stunt--
once. But not being the kind of guy who believes in doing it with the
shades drawn, I used a well-lit room, which made the effect a lot
less noticeable. Having returned to the (darkened) lab, I find that,
sho 'nuff, the screen does shimmy. To be more precise, it looks as
though it had turned into a jiggling sheet of Jell-O. Very bizarre.
Had we discovered this in the 60s it might have replaced the lava lamp.

A ripple effect of this sort is characteristic of interference
between two wavefronts, in this case the chopstick- (or spoon- or
crunchy candy-) induced vibration in your skull and the flicker of
the TV. The precise mechanism of this interference I leave to the
grad students to figure out, but it happens all right.


For info on FrameWorks, contact Pip Chodorov at <email suppressed>.