So does LED eliminate Rainbow?

Only if there are three LEDs and no color wheel. If using a single LED with color wheel, then you can still have RBE.

This is not correct at all.

An LED that also uses a color wheel does not exist. Both LCD and DLP have 3 LEDS.

Three LEDs that are on constantly in a projector, as in the case with LEDs + LCD (for example the Samsung SP-F10M and likely the CRE X1000) will not have any rainbows.

However, with DLP, there are three LEDs (R, G, B) and no color wheel. The red LED will pulse on, then green, then blue, or you could have more than one pulse at the same time to produce a secondary color, and this sequence reproduces the role of the color wheel. So, just like a color wheel, if the LEDs do not cycle through their colors fast enough, rainbows will be visible.

Reports from LED projector owners indicate there isn't "one speed" at which LEDs are pulsed. It is up to the manufacturer (and perhaps the DLP system in use) that decides the pulse rate of the LEDs, perhaps faster, perhaps slower, there is no way of knowing until the projector is in the hands of users. The Acer K11 LEDs are faster for example, with few rainbows, while it appears the new Vivitek Qumi LEDs are slower, with more rainbows.

Sisyphus,

white LED projectors do exist. Go to projectorcentral and see for yourself. They are business class projectors. Some are not made any more, but they were on the market, and yes they could have RBE.

The current round of RGB LEDs should not have RBE. Some say they can see it, but some say the moon landing was faked too. So you decide. As an owner of a Full HD (RGB) LED projector I can say it has completely gotten rid of the RBE. I used to be able to see it on my 6 segment 6 speed color wheel DLP projector... very rarely, but I could see it some times. I could see it a fair amount on 4 speed wheels and on almost all 3 segment wheels.

Correct, the LEDs are NOT constantly on in all LED projectors. All delta and Chi-lin projectors i.e. Runco, DP, Wolf, Sim2, EE Vango, etc. etc use pulsing light from the LEDs. They pulse at an amazing speed, which according to many is why RGB LED projectors look brighter than they are. I had my Vidikron 75 in the same thater as my Runco Q-750i both metered at 10.2 FL and the LED looked light 13 FL. If you read the high end threads on these projectos many including the experts say the same thing.

Here is a link for a white LED projector there are many more on pc:
http://www.projectorcentral.com/pdf/..._spec_5931.pdf

I stand corrected. To be fair, these white LED projectors w/color LCDs you reference are low lumen pico/pocket projectors, and not something people on AVS are likely to own or use for home theater.


Wow. First of all, your experience is with high-end LED projectors ($10,000 plus) whereas the majority of owners here are concerned with <$1500 LED projectors. These less expensive LED projectors do have rainbow artifacts. I'm not sure why you are so defensive. Some projectors the LEDs are pulsed faster, others slower, why is that so difficult to accept?


Maybe you can provide a link to a post but I'm pretty sure the reason everyone perceives LEDs as brighter is due to the LED spectral output being closer to the ideal wavelength sensitivity of the eye, not because they are pulsed.

For example, the ideal output for a green laser (or LED) is around 525-550nm, because this is where our eyes are most sensitive. Thus, the closer you get to this target, the greater the perceived brightness, even if both light sources measure the same lumen output.

http://www.dreamlasers.com/support/tech-laser-app.htm

I didn't perceive RT's post as defensive. I do find it funny when some people claim they can see RBE on a projector with the equivalent of 20x CW speed, using full RGB LEDs...just doesn't seem likely. The full RGB projectors above 8K are what he was referring too, not the elcheapo $1500 and below versions.

We are in the under $3,000 forum.

I see rainbows on my 3 LED, DLP projector, it definitely was not $10,000 though.

I am highly rainbow sensitive and it's quite obvious on my slow 2x color wheel Acer 720P projector, but less so in 3D mode.

I can see very faint rainbows on the QUMI LED projector, but nowhere near as what I see with the Acer or the BenQ W6000. I can't see it on the screen, only when catching a reflection when looking in the direction of the projector.

For me it's a non issue for someone so easily bothered by RBE. I want to pick up one of the 500 lumen models as soon as they released. It's great to be able to turn it on/off at will without concerns for the lamp.

Yeah I'm very sensitive as well, but I didn't see th first rainbow on the Runco Q750. Jason you missed out on a good deal. The dealer I viewed it at, put it up for sale on videogon, $5500 was a steal for that thing! If it were 4 months earlier I would have bought it myself!

So do the current led pj's have zero light on a fade to black since they can turn off?

I didn't notice zero light on the Runco. They still emit light during a movie. The actual native contrast isn't much different than DLPs using standard lamps. However the ANSI contrast is simply outstanding! They crush majority of the projectors out there in that area, some of which can't hit 300:1 ANSI. I read some where they measure over 800..nearly 900:1 ANSI! You can see it too..images literally pop off the screen! Who needs 3D? lol

Not a cost issue. High-end companies tend to listen more to the needs of their customers and deliver an overall higher quality product. Also, most or all? of these high-end projectors are using Phlatlight PT-120 LEDs and so you have to wonder if they are also sharing the same chipset or driver pulsing the LEDs at a higher frequency.

At the risk of getting flamed here I am going to say that I do not think I am at all sensitive to RBE. I never saw it on the Optoma GT 720 I had for a few weeks and never see it on my Samsung 61" RP LED TV. I never saw 3d on the 720 and returned it for that reason. My Samsung does flawless 3d in checkerboard mode but I can definitely see what looks like a rainbow in light colored screens like the sky or ice in RE. Is that what folks are talking about with RBE because I never see it on 2d sources? I mean I never see it otherwise and while it is a bit annoying, it is not enough to detract from the 3d show. I, for one, am a fan of the LED light engine. It simply rocks for me.

Consider yourself lucky if you don't see them. I love DLP but it always comes down to how bad the rainbow effect is. I had the Optoma GT720 for a while but had to sell it because of seeing RBE every time I moved my eyes.

Here's an example of what it looks like:

http://en.wikipedia.org/wiki/File:dL...bow_effect.JPG

Thanks for your input. Just trying to figure out what the picture quality improvements led provides.

I was not trying to be defensive aty all.

I do not have time to go pick out avs threads and posts for support for everything I know. No one posts documentation for everything they post. Look or search this site and you will find your answer. Go to the Runco site and the Q line they have a great article on the subject.

The reason, The Runco and or ANY projector does not fade to off is: Reference video levels state black is 16 not 0 and reference white is 235 not 255. This is to allow for foot space and head room. This means there is going to be some light whether you want it or not. If you set your projector for video levels and not film levels (Which the Runco can do) and if your BD player and or pre/pro, or AVR can output them you will get the LEDs to shut off. I can do this very easily on my projector with computer inputs, however, with film input it presents a problem on almost all projectors.

I have also seen cheaper LED projectors have not seen any RBE. I have seen a qumi. I also do not know if cheaper LED pj pulse slower. If they do it may be to show the difference between a cheap and more costly pj. Just like any projector with a DC4 technically can have the same contrast ratio, but in real world there are so many other factors that go into a pj that just the DC does not make anything an absolute.

I also agree that many here would not consider pico projectors for there home theater, however, just as many would not consider the Qumi a home theater projector due to its resolution and output. Everyone even in the below 3K area is looking for their own thing. I am not and never bash someone for the price or quality of their pj. Everyone has different means, and even if they can afford a pricey pj may not want to spend that much.

Just as some posted on here that a Q went for 5.5K, I would never and have never paid anywhere near retail for any of my eq... all bought new.

There is the CRE-X1000
LED and LCD full HD.
however this pj does not have the best contrast or colors.

I may have taken your post out of context. Sorry about that.

No problem.

This is a forum and we have to take what is written at face value, and sometimes things do not come across as they are intended. What I ment by faking the moon landing was that everyone is different and even some things that are accepted by most may not be accepted by all.

It is too bad that Vivitech "slowed" down the pulsing of the qumi. My guess and only a guess is that to have the faster pulsing they need more caps, a bigger power supply, a higher price point, and more room for it all. With such a small case they may just not have had enough space for everything and at the price point it was cost prohibited.

Video reference is irrelevent to black level. The 16-235 level is a leftover from analog video when circuitry could not be biased to zero. If you can make the PJ blacker by using the VGA input, which utilizes 0 to 255 video range, then you have a calibration problem.

The residual light projecting from the lens of a DLP projector when an input signal is calling for black is a result of scattering inside the optical engine. The Dark Chip series is the result of TI's efforts to control the scattered light, but it can't be perfect because of diffraction limits around the tiny mirrors. All other thing being equal, you will get less scattering from larger mirrors in the DMD.

The RBE issue may be the result of switching the mirrors at slower speeds in cheaper projectors. TI may charge a premium for faster DMDs, although I'm guessing here. However, the mirrors must be switched faster to sequence through the colors faster.

GS true about DMDs and about analog devices, however, if you are looking calibrating a projector using the correct REC 709 (HD) or 603 (SD) standards, if I remember correctly you will see that reference is 16. Even today it is 16 and therefore not completely black as 0 for video level. The transport cable has no bearing on the level i.e. you can get 0 out of HDMI and you can get 255 as well, but only if your pj can do video level and can be set as such.

The Runco Q series can be set for level levels (Full 0-255). The Oppo 93 can be set for video levels. However, Blu Ray Disk (BD) is encoded, if done correctly, at 16 to 235 and no matter how much a person does you will have some light on the screen. This one of the major issues with the current system.

The AVS calibration disk and links go into this as well as the S&M and DVE disks.
My projector will show 16 to 0 and 235 to 255 however they are not used by film. It does not mean there are not movies that have a 0 level in them. All I am saying is the standards require encoding within the 16-235 range.

When I use my Q as a monitor for my computer I easily get the LEDs to completely shut off.

Bsims,

It is just like all the other projectors. Take a 1000 lumen projector from different manufacturers and see if the pq, brightness, uniformity, throw, etc, etc are the same.

Unfortunately, the pj s a whole makes a BIG difference in what we see on the screen. The optics on my projector weigh more than the entire Qumi. I am not saying mine is better, bigger or anything. Just saying bigger better optics on any projector will improve the picture.

Same with a light source a 250 watt bulb is not a 250 watt bulb. Phillips and JVC are trying to design "special" bulb with specific features to improve their pj.

Even a 6 seg 4 speed color wheel projector is influenced by the other components. I have owned 6x4 and 6x6 PJs and seen many others. A good quality (fairly expensive) 6x4 can beat out a 6x6 even in RBE.

This is the main reason I will not by a projector without seeing it in person first. One is great the other so so and the last even worse, yet they have the same specs.

What you see now is not rainbows but motion blur plus color breakup. You going to see motion blur with that CRE 3xLED , only it won't break up.

Motion blur is the price you pay for extra brightness of hold type rendering, plus with sequential color it breaks up. Make DLP render like a CRT , there won't be color breakup, nor motion blur.

Yes, the reference level for black, in a video signal, is 16. Levels below 16 are blacker than black, and in a composite video signal, with a CRT display device, they provide retrace blanking and horizontal sync. The levels above 235 are whiter than white, and they provide vertical sync, if I recall my composite TV signal correctly. However, my point is that level 16 is supposed to be black, and you can't see any blacker than black. If you are seeing the blacker than black levels on your display, you have a calibration problem. You are giving up contrast in your video signal, and if your PJ is a Runco, you paid dearly for that performance.

Yes! The single-chip DLP PJ is a sequential color system. We think the problem should be solved by replacing the mechanical color wheel with electronic LEDs that can be switched in less than a microsecond. However, the DMD is also a mechanical device. The mirrors are about 10-16 microns across, and have micro-mass to match, but an electron weighs 9 E-28 grams, so they have a huge mass compared to the charges in electronic devices.

To make this worse, TI promotes a less-expensive DMD that has half as many mirrors as is needed to make a complete image. The DMD has to use wobulation to create the image, which is just a buzzword for time-division multiplexing of the image generation. This cuts the apparent switching rate in half. This may explain the apparently slow switching for inexpensive LED PJs.

GS,

The point I was trying to make and that has been disccussed in the calibration forum over and over is 16 is NOT black, with no light. I have seen DLP, LCD, SXRD, and LCOS all properly calibrated. Reference black is a name, it does not mean no light. All of the above technolgies show light at reference black levels.

My projector as well as the ones I have seen calibrated by the factory at Runco events show reference black as it should be. If you call that absolute black, then yes my projector is showing everything correct. If you are in the group that feel this created black level of 16 is not aboslute black then my projector is still calibrated correctly.

GS I agree with you on TI and their "new and improved" .65" DLPs

Many have said they are not as sharp looking and are not as fast. They have not even given them a DC number, just .65" DLP