Projection TV technology...DLP or LCD?

ReconFive · Post by **ReconFive** » 20 Sep 2005, 19:58

Hey guys.. i'm just wondering if anyone has any thoughts or opinions on DLP vs. LCD technologies for large screen TVs. I'm in the process of buying a replacement for my 200 pound 34inch CRT...and i think i'm leaning towards DLP since the black levels seem to be much better and i don't notice this "rainbow effect" i've heard about.

Is there any other reason not to go with DLP?

Thanks

tom2681 · Post by **tom2681** » 20 Sep 2005, 21:05

I'll try to explain this "rainbow effect" to you --no guarantees, though--

:

DLP videoprojectors and retroprojectors function in the same way:

-The lamp projects light on a matrix of micro-mirrors.
-These micro-mirrors have two settings: 1 and 0.
at 1 they reflect light towards the projection screen, at 0 they reflect nothing.
-Before getting out of the projector, this reflected light goes through a coloured wheel that looks like this:

This wheel rotates at a fixed speed (120 hz most of the time).

So, instead of reaching your screen in one piece (à la LCD), only 1/3 of the DLP picture is displayed at the time.

Green picture, then Red picture, then Blue picture, then Green, etc...

Thankfully, human eyes are generally quite slow, which means that your brain will reconstitute the fully coloured image instead of seeing Blue, then Red, then Green, etc...

What's this "Rainbow effect", then ?

That's easy to explain (now that you understand the technology):
If you move your eyes from one side of the image to the other (and if your eyes are quick enough), your eyes will catch either a green, blue or red image during the eye movement and your brain won't be able to reconstitute the entire image (by the time all 3 images are displayed, your eyes won't be looking at the same spot anymore).

What you will see then is a very bright (and very painful) red, green and blue rainbow across the screen.

Most people are very slow (in terms of vision) and don't notice this rainbow effect.

Beware !
-A larger screen means bigger chances of moving your eyes -> bigger chances of seeing rainbows.
-Rainbows are only visible when there is no light source apart from the projector itself.

-- Other than that, DLP projectors are top-notch --

BiscLimpkit · Post by **BiscLimpkit** » 20 Sep 2005, 22:10

Very informative post there my Kitty stroking friend.

So do you agree with Recon's statement of superior black levels on a DLP?

ReconFive · Post by **ReconFive** » 20 Sep 2005, 22:11

Thanks for the info, Tom. Very helpful

Tom2681 wrote: What you will see then is a very bright (and very painful) red, green and blue rainbow across the screen.

Wow, i didn't realize it was that big of a deal even if you were one of the people who could see the rainbow effect. If your going to see it at all, will it happen all the time? so i'll know while i can still return it?

Rainbows are only visible when there is no light source apart from the projector itself.

So, if the room is completly dark when the TV is on? (which is deffinetly the case with me)

tom2681 · Post by **tom2681** » 20 Sep 2005, 22:48

do you agree with Recon's statement of superior black levels on a DLP?

100%.
I had a LCD projector once: blacks were grey.
Up until now, I've had a DLP projector: blacks are blacker than in a movie theater.

*rainbow effect*
-i didn't realize it was that big of a deal

It's kinda like the burning sensation that you get when you see the sun with your bare eyes. Not very pleasant indeed.

If your going to see it at all, will it happen all the time?

Everytime your eyes move, yes.
For example:
-When the whole screen is black and the scene is only lit by a match or a torch: if you follow the torch = Rainbow.
-Everytime you have to look down to read subtitles = Rainbow.

-Rainbows are only visible when there is no light source.
-So, if the room is completly dark when the TV is on?

Yep, exactly.
All eyes have a tendancy to follow the light when it's dark.

----------------------
First anecdote:
I am extremely sensitive to rainbows. When I first bought my now defunct DLP projector, all I could see was a bunch of rainbows.

Rainbows usually cause fatigue or nausea.
(don't be surprised if you feel like vomiting after watching a 2-hour movie).

However, when I got used to the size of my screen, my eyes stopped moving around = no more rainbows.
----------------------
Second anecdote:
I have a friend who won some kind of lottery last year and decided to buy the biggest DLP projector he could find.
He bought a 8 000 € Infocus DLP projector.

When he went to the store to check it out, he couldn't see any rainbows.
(There were light sources everywhere, and he was too far from the screen).

He then invited me to his house to watch The Fellowship of the Ring on his new home-theater beast.
He threw up during the Mines of Moria and suffered from the world's greatest headache.
He thought he would get used to it in a few months but he was mistaken.
He did find somebody who would buy it for 2 000 € after 2 months of projectile vomiting.

The funny thing is: he never saw any rainbows, but his brain did (and couldn't deal with it).
-----------------------

Don't buy a DLP projector unless you're 100% sure that:
-you can return it after a few days/weeks of intensive movie-watching.
-your eyes are crappy enough not to be affected by the rainbows.

-----------------------------------------------

Is there any other reason not to go with DLP?

I may as well flood this forum with my unlimited knowledge (

):

LCD:

Pros: Very smooth picture.

Cons: Dead pixels:
(a bright red or blue dot that never goes away)

misaligned matrixes:
(green, red and blue pictures are not aligned correctly on the screen)
(happens very often)

vertical banding:
(very annoying vertical grey bands)

screendoor effect:
(most obvious when you're close to the TV screen)

DLP:

Pros: High contrast level.
Discrete screendoor:

Cons:

Rainbow effect:
(what you see in the animated gif is pretty much what you get)
(imagine that on a 32" screen

)

Motion dithering artefact:
Due to the lack of speed of the colour wheel, DLP projectors display a blurry trail behind moving objects, especially during horizontal panning shots.
It's kinda like what you see in badly encoded DivX videos or old Universe and Mei Ah dvds.

Hope it helps !

ReconFive · Post by **ReconFive** » 20 Sep 2005, 23:02

Holy crap, i'm really worried now

As everyone should know by now, i am EXTREMELY sensitive to any artifacts in either the video or audio of my movies. If i even started to see any form of rainbows what-so-ever the TV would be out the door for return.

I really want this DLP, but..

ReconFive · Post by **ReconFive** » 20 Sep 2005, 23:17

As for the brand of the TV itself, do you know if there is a leader in the DLP TV area. It seems that Toshiba and Samsung are the leaders of the DLP market, but i could be wrong.

I have been eyeing this Toshiba 46HM95

Its a small room, so 46in is plenty big trust me.

tom2681 · Post by **tom2681** » 20 Sep 2005, 23:19

Read my previous post, I've added lots of info in there.

As for the brand, nothing equals an Optoma projector IMVHO.

ReconFive · Post by **ReconFive** » 20 Sep 2005, 23:28

I know absolutly nothing about external projectors. That seems like it would never look as good as an actual TV..but like i said, i don't know anything about it.

Motion dithering artefact - on DLP

:x damnit, that is something i cannot stand. I thought DLP was much better at dealing with that then LCD, because of "refresh rate" issues on the LCDs.

hmmm..

tom2681 · Post by **tom2681** » 20 Sep 2005, 23:35

About refresh rates:
All I can say is that my 5 year-old LCD projector was smoother than my 6 month-old DLP in terms of fluidity.

But it's only noticeable when there is slow horizontal panning.
If you remember Fellowship:
-The long and slow panning shot in the beginning that shows the shire, then pans to Gandalf's cart going uphill towards Bilbo's house.

That shot was so blurry and jerky on my projector I had to close my eyes to end the suffering. But it's still a small price to pay for having a big picture in your room.

ReconFive · Post by **ReconFive** » 20 Sep 2005, 23:42

Well, the only reasons i wanted DLP in the first place are..
-Higher refresh rate with highly reduced motion blurring (the MOST ANNOYING video artifact ever, IMO)
-Blacker blacks

so, given this new info...i'm not sure what to do.
Either way, thank you very much Tom for your effort in explaining this crap.

tom2681 · Post by **tom2681** » 21 Sep 2005, 00:07

the only reasons i wanted DLP in the first place are..
-Higher refresh rate with highly reduced motion blurring

Not gonna happen. LCD is better than DLP at limiting motion blurring (for the time being). :x

-Blacker blacks

True.

given this new info...i'm not sure what to do.

Try before you buy.

thank you very much Tom for your effort in explaining this crap.

Glad I could be of assistance.

gojensen · Post by **gojensen** » 21 Sep 2005, 08:46

Be sure you go somewhere you can configure the monitor and brightness around it to simulate your own setting. Most monitors in store are just "destroyed" by the inability of the folks setting them up to do so correctly.

I took a stroll through the local "plasma-TV" dealer a few days ago... and well, not ONE of those screens would want to make me invest in that technology.

As for DLP it's very important you try it. There are for instance items with 3 mirrors (one for each colour) that apparently are NOT prone to rainbows (or get a projector with 3 tubes - nice but very costly

). I find that if I shake my head (or headbang) in front of the screen I quickly determine if it would show rainbows for me. I don't get sick over it, but I find it annoying - it's something that just pulls me out of the movie and I go "wtf was that?" ... maybe I could get used to it, but I didn't... I went LCD.

(There are now LCD projectors that I'd say are better than "most" DLP projectors. Even in blacks... even if they "cheat" to do it...)

But as I Tom said, try before you buy! In Norway (luckily!) there are several shops that have a 30-day return-warranty if you are not happy with the product.

tom2681 · Post by **tom2681** » 21 Sep 2005, 10:10

There are for instance items with 3 mirrors (one for each colour) that apparently are NOT prone to rainbows

Yep. 3 mirrors = No coloured wheel = No rainbows at all.
Tri-DLP are quite expensive though.

gojensen · Post by **gojensen** » 22 Sep 2005, 08:53

Are we talking budget here?

In my opinion CRT tubes are the best "tellys" still... Though Toshiba and Canon are working on something they call SED for 2007 which is essentially a huge array of smaller CRT like-emitters linked to create a big screen. Should be a lot better than Plasma/LCD/DLP screens if/when they get it working 100%. (see this url)

Man, my previous post is riddled with bad language eh? Should learn me not to post publicly so early in the morning