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Discussion Starter · #1 ·
A friend who knew I am purchasing an LT150 called me and said he just happened to have one sitting on his desk and I could come over to preview it. It was 5:30 PM and a good bit of ambient light was coming in through the blinds, enough that I could easily see in the room. The room was roughly 10' X 12', basically a cubicle with a door.


We hooked it up to a laptop via RGB and projected onto a grayish colored whiteboard from a distance of 5-6 feet or so. I guess the image was about 3 feet by four feet?

I was immediately struck by the color saturation, lack of pixel structure, and clarity of text. Then we popped in the movie "Cube" and started up WinDVD.


My immediate impressions were: "I cannot BELIEVE how rich these colors are, and those blacks look pretty darn black to me!" Then I started enjoying the movie, which I suppose in itself is a testament to the projector given the viewing conditions.


Then it was rainbow city. Me, my friend, and another bystander all three went "ugh" at about the same time. The rainbows were so bad that I thought someone was holding a prism up, I guess I saw 1-2 per second. we the shifted the projector onto the corner of the room so half the image was one one wall and half on another (the only empty wall space), just to see if the rainbows were still there. (The white paint was semigloss). They decreased in frequency but were still there.


Ok, so now I think this projector has the bang for the buck you all say it does. But I want to know if the rainbows were bad because of the highly imperfect viewing situation. To give you an idea, if I stood up to look at the reflection of the lens in the whiteboard, I felt like a flashlight was shining in my eye. That's how reflective the "screen" was. Will an actual screen decrease rainbows or am I just rainbow prone? We did nothing to look for them, they were really obvious.




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It may decrease with tweaks but will still be there on some movies. I personally have not seen one and am glad I haven't. Sorry, but you're one of the 10% with rainbows. Newer DLP with faster color wheel will less this effect for a lot more money, but you'd better stick with XGA LCD (LT154 is about the same price as LT150).


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Huey ;-]
 

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Discussion Starter · #3 ·
All three of us saw them. Does that mean all three of us are in the 10%?


I will definitely try to audition an LT155.




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I don't own one of these things (though I'm hoping to get one in the not too distant future), so take what I have to say with a grain of salt...


Some of the proposed causes of rainbows:

1) Specific to individuals.

- You're situation would seem to disprove this. At the least, your situation seems to prove that under certain scenarios, rainbows will be visible to most/all.


2) Worsens with high-gain screens.

- Seems to be disproven due to the high number of people pairing this pj up with the Da-Lite High Power who see minimal or no rainbows.


3) Caused by eye movement. Eye movement should increase the larger the screen size (or closer you are to the screen).

- I think enough evidence exists to support this one. But you're post (and another recent post by someone else) would indicate that this may not be the only cause for rainbows.


So, here are a few new possibilities I'll throw in to the mix...


4) Small screen sizes. We're pretty sure that big screens result in more eye movement which result in rainbows. Small screens should have little eye movement, but perhaps they cause rainbows for a different reason.


5) Lots of ambient light.


I think it would be a great idea for someone to test these theories (and any other obscure theories they can think of). Maybe we can nail down the causes for rainbows (at least with the L150) once and for all.


Scott
 

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Did you happen to turn off the white segment for this test?


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Huck
 

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Right now I'm running the LT150 on a white sheet with a screen size of about 115". I'm 13 feet back. It is being fed by a non-progressive dvd player and using composit out. So truly the worst type of connection and output for this projector. I put in X-men and watched the titles. I moved all around the screen and I think I might have seen a rainbow but I couldn't duplicate it. I watched the fireworks. nothing. I popped in Gladiator, nothing. So I'm glad to be one of the 90%. http://www.avsforum.com/ubb/smile.gif


I did move closer to the screen and I did see a few more rainbows in X-men. But I was so close that I had to move my entire head to go from far left to far right. My HTPC should be built soon so I will have a better image to compare with but I'm no longer worried about rainbows even though this board was making me nervous right up until the projector came in the mail.


Now everybody shhhhhh, don't tell me any more flaws. lalalalala, uh lalalalalala http://www.avsforum.com/ubb/biggrin.gif
 

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Another theory -


Maybe you can become "rainbowacclimated" over time.


When I watch the LT150 for a while, I still notice the rainbows, but not as much. However, when I watch the D-ILA for a while, and then switch to the LT150, I see rainbows everywhere.


It might have to do with "What you are used to" as well. Without anything to compare it to, the rainbows are much less pronounced. When compared to a 3-primary device, the rainbows are very obvious and not at all subtle.
 

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What Rainbows?


LT150 & HTPC
 

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im have a lt150 with htpc and although i haven't used it much, maybe only 15 hours (had to leave on a trip, miss my projector) i haven't seen any rainbows either
 

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I would definitely try projecting onto a lower-reflective surface before making up my mind about rainbows.


When I walk beside or past the front of my LT150 when it is projecting, I catch lots of rainbow effect around the lens of the projector. I would imagine that a moderately reflective surface (such as that of a white board) would create a similar effect as that of looking towards the lens.


I see rainbows in high contrast scenes in movies, but not enough to bother me much. I think I have also started tuning them out as I've watched more and more.


On the other hand, my wife has never commented on seeing anything strange, even after I asked her if she ever saw flashes of color.
 

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Discussion Starter · #13 ·
No, I don't believe the white segment was off. I opened the box, pulled out the projector, plugged it in and turned it on.


The screen size must have been small by any standards, the projector was perhaps 5-6 feet from the wall, projecting about the size of a poster turned on it's side. Maybe 3 feet across, 4 at the most. we were standing directly behing the projector.


There was uncontrolled sunlight leaking in through the blinds, enough that I could easily read/see in the room.


If I had to make a guess, I would say that projecting onto a flat, hard, smooth, reflective whiteboard could have had something to do with it. Also, I made no tweaks whatsoever in either WinDVD or on the projector.


Another point: the image was shaped like the keel of a ship, really skewed. I held the LT150 in my hands once or twice to make the image square, but most of the time it was waaaayy skewed.


I want to get to the bottom of this, preferably before I buy. I am attempting to set up an A-B between a Sharp Notevision LCD and the LT150 on an actual screen in a fairly dark room. That should go a long way towards a solution. Will post results of course.




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Try running a home theatre pc. It should reduce rainbow considerably. Our experience using a progressive scan dvd player vs a htpc showed a considerable drop in rainbow.


Warren
 

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Maybe I'm one of the unlucky "super rainbow sensitive" types.


My setup:


Digital Connection Marquee HTPC, fully decked out.

Stewart Grayhawk "low gain" screen

NEC LT150 (or JVC G11) projector.


When using the LT150, I see plenty of rainbows. Low gain screens and HTPCs don't solve it. I think that this projector is a fantastic deal, and am definitely not knocking it (if I didn't like it, I wouldn't still have it!)...I just wanted to let folks know that an HTPC won't solve a DLP's rainbow issue before they dish out the $$$ to buy one.


AFAIK, the only absolute cure for rainbows is to lose the color wheel. Since the wheel does allow prices to be otherwise lower, this isn't a great option for most.
 

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I had serious rainbow issues when I originally got the LT150, running DVD through an Iscan Pro. Then one day I hooked up my dreamcast VGA box and said "wahhh? where did the rainbows go?". I was baffled, the rainbows were MUCH more difficult to see, even in high contrast scenes. Before I would noticed them in normal viewing, but now I had to shake my head violently back and forth to see anything.

THEN I got the new Crystal Image VS 4.0 scaler and hooked it up. SAME THING, the rainbows are MUCH more difficult to see than with the Iscan..what the hell is going on here?
 

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so this whole rainbow issue... can someone take a picture and post it?


i'm curious as to what you guys are talking about.

thanx


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Since it is caused by eye movement and how your brain processes, I'm not sure you can take a picture of it. Maybe someone could produce a graphic simulation?


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Maybe if you jerked the camera at just the right instant it could be captured(maybe on a credits screen). I also use both a HTPC and a prog scan DVD and see no difference in rainbows. I can see them easily on either but usually don't think about them.
 

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I tend to agree with John above, that you are not going to be able to capture this phenomenon of rainbows in a photo, because it is a matter subject to optical perception. I have used nearly all types of projectors over the past 10 years or so and have recently experienced the LT150 DLP, having gotten in on the Dell deal. I immediately experienced the rainbow perception. I didn't find it terribly distracting but distinctly certain. I did notice the effect somewhat reduced when projecting on a low gain screen material. I much more troubled by the loud fan (ceiling mount) than the rainbow effect.
 
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