Projector Latency…
18 December 2007
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Latency is a time delay between the moment something is initiated, and the moment one of its effects begins or becomes detectable. When it comes to projectors, latency refers to the time difference between the computer screen and projection from the projector. There will always be some latency (time difference) between the source image (computer) and the displayed image (projector).
Laurence Muller has a Beamer Latency Measurement Tool v0.2 that will measure the latency of the projector. Ideally anything under 20ms is really good. For multitouch, if the latency of the projector is high, there will be visible lag between finger movement of objects and the projection of these objects.
Here are the screenshots of my projector (Casio XJ-S30) and notebook performing the Beamer Latency tool. It’s simple to use. You load up the program on your computer and set the refresh rate to 60hz, mirror the image on the projector, and take a picture with camera set on 1/60th. Since the display is running 60fps (fixed in opengl gamemode) a delay of one bar means 1/60 sec = 16.667ms.
As you can see, my projector (Casio XJ-S30) has less than 1 bar latency which means I have less than 20ms latency which is great. I recommend this tool when testing projectors.
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wait.. you didn’t just use an lcd screen as measurement instrumentation for latency, did you?
*facepalm*
Huh?
I’m using a tool to check the latency of a projector display, not an LCD.
What S means is, yes, your Projector is 16 ms behind your LCD screen, but how much is your LCD screen lagging? That’s why people usually test their LCD/Projector against a CRT. It’s the lowest latency output device.
I have documented some multitouch and projector latency tests here: http://mue.music.miami.edu/wiki/index.php/Multitouch_latency_tests
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