Can't argue with someone who can write like this. Knowledgeable.<br>Mental note: google before communicating with mjg59 ;)<br><br>(I guess this subject (preemption) was discussed for too long already)<br><br>BenC bring it on!
<br><br>Regards<br>Flavio Martins<br><br><div><span class="gmail_quote">On 11/29/06, <b class="gmail_sendername">Matthew Garrett</b> <<a href="mailto:mjg59@srcf.ucam.org">mjg59@srcf.ucam.org</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
On Wed, Nov 29, 2006 at 12:27:25PM -0500, Phillip Susi wrote:<br><br>> No, this is the beat again. You are being shown images that show the<br>> wheel more than 180 degrees out of phase with the previous and next<br>
> images, which is the same as if it were going backwards at a slower<br>> rate. If the wheel is spinning at 23 rpm and the film is 24 fps, then<br>> you get a 1 Hz beat.<br><br>If the human eye is unable to distinguish movement at faster than the
<br>equivalent of 24 frames per second, then you'd see exactly the same<br>thing in real life. You don't, which indicates that faster movement is<br>still perceivable. In computer games, the difference between 30 frames<br>
per second and 60 frames per second is quite easy to distinguish.<br><br>In reality, there is no concept of "frames per second" in the human<br>visual system. The eye receptors are sufficiently sensitive that a<br>
single photon will produce a visible response[1]. The fact that we<br>perceive 16 frames per second as smooth motion is an artifact of<br>higher-level processing, not an indication that we're unable to perceive<br>flicker above 16Hz - there's no well defined lower bound on the minimum
<br>period of time a stimulus has to appear for before it reaches higher<br>levels of consciousness, and it varies between individuals. Even with<br>continuous flickering (a worst case scenario for determining whether<br>
a stimulous is continuous or not), some people are able to perceive<br>120Hz flicker.<br><br>> What are you talking about? The light source in the projector is always<br>> on and 24 film frames pass in front of it each second. Where is the
<br>> double illumination?<br><br>If that were the case, you'd see the frames moving vertically. You<br>don't. There's a shutter between the light and the film, as described in<br><a href="http://en.wikipedia.org/wiki/Movie_projector">
http://en.wikipedia.org/wiki/Movie_projector</a> . On modern projectors, the<br>shutter opens more than once per frame.<br><br>[1] Sadly the spontaneous firing rate is higher than this, so a single<br>photon is somewhere below the noise threshold
<br>--<br>Matthew Garrett | <a href="mailto:mjg59@srcf.ucam.org">mjg59@srcf.ucam.org</a><br><br>--<br>ubuntu-devel mailing list<br><a href="mailto:ubuntu-devel@lists.ubuntu.com">ubuntu-devel@lists.ubuntu.com</a><br>Modify settings or unsubscribe at:
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