How afraid should I be of RBE? - Page 2

So how does one lean see a rainbow? I know Captain Noah can sing a rainbow! (oops dating myself) but for the life of me, I have only seen them in the sky. I have been watching DLP projectors IN72, HC3000 and even a Dell 3400 for that past 5 years and can't seem to see them... even eating popcorn! Guess I need glasses.. wait I already wear glasses.. WHATS WRONG WITH ME!!

I believe Temporal Chromatic Distortion (TCD) is a more accurate way of describing the “Rainbow Effect”. Let’s face it RBE sounds quite innocuous and even cute. The full colour images of DLP technology are created by strobing the three primary colours (red, green, and blue) on a DMD (digital micromirror device). The strobing occurs so quickly that the human eye should only see one image.

The outline distortion results from the lag in the strobed colours. Instead of seeing a solid object one sees an object and a trail outlining that object that consists of the red, blue and green. Although the effect is called the “rainbow effect” I have only seen the primary colours: red, blue and green. Lighter objects are silhouetted against darker objects.

All my viewing rooms have white walls and my LED projector TV is rated at a maximum of 300 lumens and 1000 contrast. I see the chromatic distortion. (I believe any mention of contrast should include the viewing environment because walls, carpeting, projector light leakage, and even clothing can dramatically reduced contrast.)

I chose LED DLP because I prefer the image quality of DLP over LCD. The colour saturation is much better. My Epson 720HC projectors produce excellent pictures but my concerns about bulb life makes it impossible to enjoy the picture.

As noted, I see the TCD/RBE on my 300 lumen 1000 contrast ratio projector. Thus, high brightness and contrast (Someone, please define “high”.) are NOT required to see the effect. There is a difference in LED and Halide TCD/RBE and that is the brightness of the effect but not the effect.

The fact that a faster strobe speed reduces the effect indicates that it is a temporal (time) based problem.

I have noticed that the outline distortion seems related to the warmth (closer to the 6500k temp) of the video image. For example, when I watched the Taken mini-series I was constantly distracted by the effect. The common factor was the autumn colours in many scenes. I then noticed that warm colours seem to produce the effect. I usually prefer a cooler (7000k temp or higher) picture so I am less distracted by the colour lag.

I must note that the absence of complaints does not provide enough information as to whether or not a person is going to have an unpleasant experience with TCD/RBE. Substantial numbers of people could have health problems with the colour strobing of single DLP technology and we would not know. If a person does not recognize a problem or the problem immediately goes away then is there a problem?

My standard for home entertainment is distraction. I am not seeking nor can I afford the latest state of the art technology. When I first watched DLP projectors I was tremendously impressed but watching the lagging images proved extremely annoying. When the strobe speeds increased then I was not as bothered.

I suspect that if you are light or colour sensitive (I believe gender and age affects colour and light sensitivity) then you might find the strobing distracting. I suggest a simple test: gently fan a white index card a few centimeters in front of a DLP projector that you are considering purchasing. I speculate that you will see the red, green and blue outlines. Rotate the card ninety degrees and try again. If you are greatly annoyed by the pulsing red, green and blue my speculation is that there is a movie or two that you will not enjoy on that projector. You will probably get eye fatigue but you should be able to enjoy a movie.

With the longer lamp life, I am looking into the newer generation of DLP 3D projectors. I have been reading the BenQ 1070 thread. I intend to follow the BenQ1080st thread and the Acer 6510 threads when they arrive. Although I am very sensitive to TCD/RBE, I suspect that the absence of complaints of a severe nature means that I will probably try a lamp based DLP projector for very casual movie viewing.

So to respond to your query: yes you should be concerned. But since you are considering DLP projectors and not DLP projector TVs (with longer viewing sessions) then I would just say carefully look for any hint that TCD/RBE maybe a problem with the projector in which you are interested and definitely preview (if possible) before buying.

I've found a simple solution for RBE problem (i have Optoma HD66). In front of lens of my projector I've put two circular polarizer filters (52mm). By rotating one of those, I can change brightness of picture. Picture is slightly dimmer, but without rainbow effect (at least I cannot see it anymore).

I've not found a single person yet that can see substantial RBE on the Benq w7000 when it is in 6x color wheel speed at around 15 fL. Yes, if I run a certain test on a computer desktop some of us can see it but it's not the same effect as seeing it on a 4x or slower wheel. Also, there are people that just cannot see it even on a 4x wheel, it's partly brain chemistry or eyes. Most younger people see it easier than older people so I've noticed.

I would not worry about RBE on a 6x color wheel unless you plan on watching the projector in torch mode, anything slower than 6x and you need to test for it.

Basically on a 6x wheel it goes by so fast even when you do see it in a test, that most people's eyes have trouble picking it up in normal viewing, sometimes you have to re-run the test several times to see it even when moving your head. Both my friend and I found the Mits hc4000 unwatchable in some scenes due to RBE (4x wheel), but not so on a 6x PJ at all. When it is detected by someone on some PJ's in the 6x mode, well first off it's usually a much smaller looking area where they catch the flash, and it's usually on the edges of the image instead of a big square or circular like flash in the middle. So it didn't bother anyone yet. Actually the w7000 has lower contrast in dark scenes so even the 4x mode doesn't bother me.

I do admit though some higher-end DLP projectors that have higher contrast like a Runco or Marantz might be easier to catch RBE on even at higher speeds, but some of those have even more tweaked out CW's.
Edited by coderguy - 3/15/13 at 4:36pm

@Coderguy, I have a few questions.
1. When you see RBE, are you momentarily distracted and then able to quickly continue enjoying what you are watching?
2. I am very hesitant to ask (sometimes for me knowing is NOT better) but you imply that there is a “test” for RBE. Is it a standard or a personal test?
3. On the Benq w7000, you say that it is a 6x colour wheel. Isn’t the Benq w7000 a 3D projector that projector that time multiplexes its 3D images? If so then what is the effective wheel speed in 2D and 3D?
4. My Epson has an auto iris feature that I have to turn off because it is annoying listening to the constant movement. The 6x wheel speed is well within the audible range, is the Benq (or any higher speed) colour audible?
5. Is 6x the actual wheel speed? If the wheel has duplicate segments; rotates at 3x and flashes each segment twice per revolution would that be a 3x wheel?
6. Finally, I don’t have to have an object on my screen to see the effect. As I entered the family room I noticed the boundary between the screen and wall showed the lag (I was about forty feet from the screen). Do you only see RBE when you have an object on the screen?

1) Well, yes it is a momentary distraction but if you are seeing it bad enough it can sort of hurt your eyes a little if the flashes of RBE are bright. If you are watching too bright of an image, when you see it is sort of like someone taking a picture of you with a camera flash that has rainbow color (not quite that bad, but you get the point). Most of time you see it as a flash in the shape of a line or square or circle on the screen after fast moving motion in a dark scene with bright lights.

2) The best test is just watching content or taking a PC with a black desktop and moving the mouse fast. Stargate Universe series is a good test because it has a lot of bright lights in dark scenes. Pretty much any scene with bright lights in dark scenes, like car headlights at night coming towards the camera or the ending credits of a movie. That is what causes it, high contrast shots. That said, the only way you'll know for sure if it bothers you is by spending a few days with it usually, otherwise you can make the wrong judgement fairly easily.

3) It depends on what Hz you are in to how fast the exact number of rotations go by per frame, but the rotational speeds themselves get to 15k+ RPM just like a HD motor (actually there are some slightly faster). The number of rotations is just calculated by how many times the same segment goes by per frame. The more segments you add does not cause a different speed, it just means higher segments is better because the amount of time the wheel spends on each colored segment is shorter. For the w7000, the max speed is 6x in 60hz, and 3x in 120hz. The reason you say 3x in 120hz is because twice as many frames go by in relation to the number of rotations of the wheel, but the RPM of the wheel is still turning at the same speed. The number we go when comparing different color wheel speeds is the 60hz mode, which is why the w7000 is a 6x wheel. You can change the color wheel speed in the service menu. The color wheel speed in 3D and 2D by default is 4x unless you change it in the service menu, but even the actual RPM speed changes slightly between 24p and 60hz mode (hence you can see slightly more RBE in 24p modes).

4) Yes, the IRIS can be audible but I suppose it depends on how quiet of a unit you get as there seems to be a unit-to-unit variance.

5) See Answer # 3.

6) Well, you can see RBE when bright whites and dark blacks mix mostly, but sometimes you see it on a plain black screen as well even with no objects on the screen (even before the credits roll for instance).
Edited by coderguy - 3/15/13 at 10:25pm

Cyprus has me totally overwhelmed as I read everything on the crisis that I can. I can not process much. I just want to thank you for replying.