I´ve recently discovered that I´m heavily affected by the rainbow effect 'RBE' produced by DLP projectors. I don´t notice it that much due to the motion in the video itself but when my eyes move rapidly across the image. This is quite annoying when watching movies with subtitles, as your eyes are constantly moving up and down and the subtitles have usually high contrast, which increases the chances of perceiving the RBE.
So while trying to figure out which DLP projectors, if any, could be better, and how to improve my experience, I have not been able to find an objective measure of how much RBE a projector may produce. That´s understandable, given that RBE is a subjective issue and many people can´t perceive. However, it seems that manufacturers advertise the projectors as having 4x or 6x speed color wheel, or having a RGBRGB wheel instead of RGB one, etc. But what does that exactly mean? Is a 6x speed wheel from two different manufacturers running at the same speed? How does DLP work with LED projectors, which don´t have colour wheel, because several people have reported to have perceived rainbow artifacts.
If my understanding is correct, the underlying reason for the RBE is the fact that with DLP technology each pixel´s R,G,B channels are not displayed simultaneously but sequentially. So the number of segments in the color wheel and the wheel speed directly affects the refresh rate of each colour channel per frame. So, in my opinion, what manufacturers should explain is how many times each channel is refreshed per frame.
In order to try to find out a little bit more I did a quick test, recording the test pattern of a BenQ W1110 with a 120fps camera. When moving the camera abruptly from side to side the same RBE that I see when I move my eyes across the image is clearly perceptible. Here is the video, there are a few good examples from around second 0:49 (playing the video at reduced speed helps):
Now, looking at the attached snapshot from the video, we can clearly see how the vertical white lines are decomposed in their RGB components when moving the camera from side to side. In the snapshot there are clearly two groups of RGB components per line in the pattern. Since the video is recorded at 120fps and each colour channel is refreshed twice per frame (from what we can see in the picture) we have a channel refresh rate of 240Hz. From the BenQ W1110 specs I got that with a 60Hz video mode (which is what is what set) the colour wheel runs at 4X. So if we consider that 4X speed means that the pixel colours are refreshed 4 times per frame I guess everything makes sense as 60Hz video and 4x pixel refresh per frame gives us the 240Hz pixel/colour channel refresh rate that I have estimated.
What do you think? Does any of the above make sense?
If so, I wonder why manufacturers won´t just tell use the RGB channels refresh rate. Now I know that I can´t deal with the 240Hz colour refresh frequency of the BenQ but there is now way to find out what are the figures for other manufacturers/models. For example I would like to know whats the colour channel refresh rate in a LED DLP projector such as the LG PF1500 but there is no way to find out (I asked the technical service, but from their answer I don´t think that whoever answered me even knows what RBE is).