Consolidating a discussion that has been going on in various individual projector model threads, a question is being debated about how DLP XPR 4K pixel shifting affects color wheel speed rating and its effect on producing the DLP rainbow effect (RBE) that some are more sensitive to than others. Currently all projector color wheels are rated at 7,200 rpm, so that's their actual spinning speed. But projector companies that rated native 1080p RGBRGB color wheels as 4X are now rating XPR pixel shifting models with RGBRGB color wheels at 2X.
This is an important issue for consumers because the X speed rating has traditionally only been used to inform consumers that the higher the X number the less chance of seeing RBE (see color wheel history below). Yet the consensus of professional reviewers and owners to date has been that there's no greater likelihood of seeing rainbows on XPR pixel shifting projectors with 7,200 rpm RGBRGB color wheels rated 2X than there has been on native 1080p projectors with 7,200 rpm RGBRGB color wheels rated 4X.
will be addressing this issue in a briefing he has scheduled with BenQ this month. Forum member
has addressed the question to his contact at BenQ and is currently awaiting a technical answer while
has also been active in getting color wheel performance data from his contact at BenQ. So we're still awaiting the definitive technical answer to why XPR models are only rated at 2X even though they are apparently no more susceptible to creating RBE than similar 1080p models. When that official data is available it will be posted in this thread.
Color wheel history:
The first DLP projector color wheels had one set of RGB segments spinning at 3,600 rpm. When the industry doubled the standard RGB color wheel speed to 7,200 rpm to help reduce RBE they referred to that as 2X speed or double the original (1X) speed. Then they came up with the idea of doubling the number of RGB segments to RGBRGB, which effectively doubled the 7,200 rpm RGB color wheel speed to 4X because R, G and B segments were being flashed twice for each actual wheel revolution. In other words they doubled the X speed rating either by doubling the color wheel's rpm or by doubling the number of sets of RGB segments.
The actual speed at which the color wheel is spinning is defined by the revolutions per minute (rpm). The effective color wheel speed in terms of reducing the rainbow effect is defined by rpm combined with the number of sets of RGB segments. So the first instance of doubling color wheel rpm from 3,600 to 7,200 was an actual speed increase while doubling the number of sets of RGB segments to RGBRGB was a virtual speed increase only in terms of the number of times R, G and B segments were flashed per revolution.