Originally Posted by 3DBob
120hz DLP 3D is 60hz per eye--Left eye clear when Right black and vice versa. Most 3D projectors now do 144hz to avoid judder since 144/24= 6, therefore each eye is open an even number of times per sec=72hz. Don't confuse frames per second with hertz. With 72hz per eye, each eye opens/closes 3 times for each frame of a 24fps movie, creating a smoother sync.
4k projectors with XPR make a sound when the XPR kicks in and vibrates the chip to produce a 4K image and stops vibrating when in 3D mode to produce a 1080p image. I think that's the noise you are talking about. The color wheel is always maintained at a constant speed that I know of on a DLP projector.
Thanks, Bob, but can not bring together 144Hz and constant color wheel speed and no judder.
There is plenty of mentioning of newer projectors using 144Hz for 3D, and DLP glasses support up to that frequency, so lets go with that. That would be an improvement over the 96 Hz i have on my 5 year old Sony LCOS projector.
With 144 Hz the color wheel would have to rotate at a minimum of 60 (seconds) * 144 "frame/sec" = 8640 RPM if each displayed "frame" was a full rotation, or 8640/2 = 4320 RPM if each displayed "frame" was just one RGB(S) color wheel sequence (half a rotation).
If you make the calculation of how many RPMs you would need for other 3D (720p60) or any 2D resolution (24Hz, 50Hz, 60Hz), you end up either with judder, or with different RPM of the color wheel. Eg: If you have 144 "frame" / sec, you couldn't show 60 fps videos without judder (or 50Hz).
Hence i am hoping that the color wheel is actually spinning at a speed depending on the video mode, or else i am expecting judder in the video.
Whether or not i would actually be able to hear a difference for the different color wheel speeds, i don't know (yet). You may be right that most mentions of undesired noise from XPR projectors only comes with the pixel shift actuators.
Of course, i would very much hope for different RPMs of the color wheel,