Re: how much of what we see is black?

From: Jonathan Walley (email suppressed)
Date: Tue Oct 30 2007 - 09:16:33 PDT

My understanding is that we spend half our time in darkness and half
"in light" while watching a film. As for what we do with the rest of
our time, the ratio varies :-).

I thought that it didn't matter what sort of projector was being used -
a two-blade shutter flashes each image twice with corresponding
durations of darkness, while a three-blade shutter flashes each image 3
times with corresponding durations of darkness. Either way, the
light/dark ratio is still 1:1. What matters is "bumping up" the number
of flashes to at least 48/second (72/second with three-blade
projectors), as this crosses a perceptual threshold beyond which we
don't see flickering light but a consistent light source. I don't think
the gauge of the film/projector matters.

This is what I've read, anyway, and it's what I teach. I'd love to hear
other people on this matter, esp. if any of the above is wrong or


Jonathan Walley
Assistant Professor
Cinema Department
Denison University
Granville, Ohio 43023
email suppressed

On Oct 30, 2007, at 9:53 AM, Yoel Meranda wrote:

> A question I'm curious about...
> When a film projector is running, what is the percentage of time the
> light is interrupted by the shutter? In other words, what percentage
> of what we see is darkness?
> I realize that this question will have different answers for each
> projector...
> I am mostly curious about 35mm projectors but any clue on any other
> projector would be great. Even guesses would be fine if no one has
> concrete answers.
> Thanks,
> yoel
> __________________________________________________________________
> For info on FrameWorks, contact Pip Chodorov at <email suppressed>.

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