[opendtv] Re: Cinema explained by persistence of vision : a myth
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 18 Jun 2010 18:05:31 -0500
Olivier Houot wrote:
> Hence, explanation of cinema does not require any specific analysis
> of the brain behavior, it is just standard sampling theory.
Hmmm. I'm not a film professional by any means, but I think this question is
more math/engineering related.
I see no contradiction here. In order to understand how the eye/brain decodes a
sampled signal, you need to do this analysis of brain behavior.
It seems to me that sampling theory requires sample and hold (for a very short
time, but long enough that the sample can be stored accurately) during the A/D
conversion process, and then low-pass filtering of the sampled signal train in
decoding, to recreate the continuous signal. And sampling theory also assumes
that the original continuous signal is in fact a continuous signal (i.e. max
frequency content of signal less than half the sampling frequency). Not
unrelated images or unrelated bursts of noise.
In sampled audio, if the sparate audio samples occur so frequently that the
bandwidth of hearing cannot detect the discontinuity, the sound is perceived as
a constant tone. The ear/brain behave as the low-pass filter of the decoding
process. But of course, the samples must be related, or the decoded signal
would just be white noise. So, doesn't this require brain behavior analysis?
In visual perception, I think it works the same way. If you interpret
"persistence of vision" to be the required sample and hold in the A/D
conversion process, then there's no disagreement here. You take multiple
samples over time. If the subsequent samples are related to one another, and
occur quickly enough that the brain cannot decode them as separate images (like
audio samples occurring at higher rate than the ear's bandwidth), then the
image is interpreted as motion. But if the samples are unrelated, or are too
slow, then the visual process will perceive distinct images (or just mush).
I agree that POV alone is not enough to explain the phenomenon, but I think
that POV is one of the elemnts you need in the process.
Bert
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