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antorsae
Joined: 16 Jul 2006
Posts: 297
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| Posted: Sat Apr 10, 2010 9:01 am Post subject: LED PJs from the perspective a CRT die-hard fan |
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Hi,
A few days ago I had the pleasure to watch some hi-end DLP projectors:
- DPI Titan II, dual-lamp, 3chip, DLP projector which does both 2d and 3d.
- M-Vision (IIRC) LED-based 1-chip DLP projector.
I have a CRT blend so I am pretty picky about image quality in mostly all facets.
3d with active glasses requires a lot of light so the 3-chip dual-lamp projector does a good job. I am not a fan of glasses (maybe it they had soft-lenses instead???); the image was great, bright but the on/off contrast was not there and black level in dark scenes was too distracting for me (I must say I was the only one in the audience bothered by this)
The one this that to me is very promising is LED projectors. Colors were great, like CRT, completely silent, not to bright (today) and 1-chip DLP was perfect convergence except for lens issues... and I didn't see any rainbows! THis was did not have light modulation (iris effect) so no FFTB ... but they'll be there. This is a 1st gen projector but I think that my next setup will be a LED one once they are bright enough and have (minimum) temporal light modulation (FFTB) or (ideally) zone-based light modulation (what they call local dimming)
Again... not there yet but this looks like the technology to combine the best of CRT and the best of digitals!
Have you seen any LED-based PJ? What do you think?
rgs - Andres
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donaldk
Joined: 17 Jun 2008
Posts: 308
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| Posted: Sun Apr 11, 2010 1:17 am Post subject: |
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I have seen that DPI at ISE, too dim, even on a small screen, eventhough the slide it was showing claimed 1000 ANSI Lumens (not out that Engine it never will). Uneven light on the screen, but there might have been some reflections issues here.
Missed a couple of others. Did see the FL32, on a very small screen. 500 lumens max. Remarkably saturated greens.
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Sun Apr 11, 2010 1:31 am Post subject: |
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I've never seen a rainbow on any DLP projector - not on the screen.
If I move my eyes fast past the actual lens I can see a rainbow, but that's looking INTO the lens, not at the screen.
Andres, it sounds like you needed darker glasses. When I saw Avatar black was *almost* black (exit lights...), because the glasses soak up some light, yet it was still bright with plenty of pop.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sun Apr 11, 2010 2:16 am Post subject: Re: LED PJs from the perspective a CRT die-hard fan |
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| antorsae wrote: | (ideally) zone-based light modulation (what they call local dimming)
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I'm curious what you mean by this. Local dimming is for LED based LCD flatpanels. A LED projector would not have this type of feature. The DMD would be in control for areas of the image.
Did you hear of or read this somewhere? Where was this featured discussed in your assessment?
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Sun Apr 11, 2010 3:04 am Post subject: |
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They can modulate the output from the LED light cannon, before it hits the DMD.
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WanMan
Joined: 19 Mar 2006
Posts: 10270
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| Posted: Sun Apr 11, 2010 11:45 am Post subject: |
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LED for front projection isn't achieving anything more than maybe limited light modulation. Its application is still based on light having to be blocked instead not generated in the first place when not needed.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sun Apr 11, 2010 1:21 pm Post subject: |
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| Mark_A_W wrote: | | They can modulate the output from the LED light cannon, before it hits the DMD. |
Hmmm, this is also something I have not seen, heard or read. Where did you see this Mark?
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Sun Apr 11, 2010 1:32 pm Post subject: |
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They could only modulate the light on the whole image, since the light hits the whole DMD at once. I don't see how they could do any kind of zone-based modulation. I think at best it would be similar to a variable-iris implementation.
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WanMan
Joined: 19 Mar 2006
Posts: 10270
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| Posted: Sun Apr 11, 2010 2:00 pm Post subject: |
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| macgyver655 wrote: | | Mark_A_W wrote: | | They can modulate the output from the LED light cannon, before it hits the DMD. |
Hmmm, this is also something I have not seen, heard or read. Where did you see this Mark? |
I think he is saying you can do this, but not necessarily is being done in projector design. LED dimming from modulated (PWM) pulses seems to be available in some respect down to the 1ms scale, and some reading (Google) shows switching frequency in the MHz range.
But, using dimming LEDs is an interesting concept when applied to LEDs of more than 3 colors. Mr. Sulu may just go all WOW! on us again.
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Sun Apr 11, 2010 3:49 pm Post subject: |
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Modulating the pulses doesn't do much good when you're illuminating the whole DMD at the same time. You'd have to have some kind of scanning setup to benefit from pulse modulation -- and if you did that, you'd just modulate the LEDs to the signal, just like a CRT.
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WanMan
Joined: 19 Mar 2006
Posts: 10270
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| Posted: Mon Apr 12, 2010 11:47 am Post subject: |
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I guess I was looking at it more like at 96Hz refresh rate (for the CRT'ers) then you are looking at something on the order of ~100ms. If you modulate to something like (4+6)ms On+Off modulation than you could vary the LED output (every 100ms) by an order of 1-10. But some of these LEDs are being modulated at time intervals <<<10ms.
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emdawgz1
Joined: 14 Mar 2006
Posts: 7949
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| Posted: Mon Apr 12, 2010 1:24 pm Post subject: |
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I just saw an LED pj and i wrote about it here....
https://www.curtpalme.com/forum_archived/viewtopic.php@t=20929.html
Gentlemen.....I have seen the future......
And I think it's LED projectors.
While I was in florida I picked up a HT mag and it reviewed a M-vision Cine LED Projector... It sounded good.
So today i was at my old shop looking at speakers and iI mentioned LED Pj's and the guy sys "Yeah we just got the Runco 2 days ago. It's in here..."
So we go in and he fires up the Runco Q-750i.
Now please, no comments about Runco or whatever. I'm just talking about the tech...
It was fresh out of the box, no calibration at all. The manufacturer specs a pure white screen. Light controlled room, 'cause it wasnt real bright. We watched "National Treasure 2" on the kaleidescape( i wont go into how nice that was)
What I'm shocked to say was that it had black levels....REAL LIVE BLACK LEVELS......
it was good. Has anyone else seen an LED PJ???
What do you think.
http://www.runco.com/_webapp_2714306/QuantumColor_Q-750i
http://www.soundandvisionmag.com/hdtvs/3312/digital-projection-m-vision-cine-led-projector.html
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Apr 12, 2010 2:47 pm Post subject: |
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And if I were to say that even LED projectors are not capable of a true black......what would you say? 
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perisoft
Joined: 29 Aug 2007
Posts: 2920
Location: Ithaca, NY
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| Posted: Mon Apr 12, 2010 3:05 pm Post subject: |
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| macgyver655 wrote: | | And if I were to say that even LED projectors are not capable of a true black......what would you say? |
That you don't know how they work?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Apr 12, 2010 3:08 pm Post subject: |
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HAHAHAHAHA
Try again.
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perisoft
Joined: 29 Aug 2007
Posts: 2920
Location: Ithaca, NY
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| Posted: Mon Apr 12, 2010 3:15 pm Post subject: |
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| macgyver655 wrote: | HAHAHAHAHA
Try again. |
Given that they can just turn the LEDs off to generate full black, I fail to see how they can't match the on/off ansi of CRT PJs. And the runco specs mention infinity:1 on/off - while having seemingly sane specs for other contrast levels.
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emdawgz1
Joined: 14 Mar 2006
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| Posted: Mon Apr 12, 2010 3:41 pm Post subject: |
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| macgyver655 wrote: | | And if I were to say that even LED projectors are not capable of a true black......what would you say? |
I dunno.... It looked good to me.....
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Apr 12, 2010 3:46 pm Post subject: |
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| perisoft wrote: | | macgyver655 wrote: | HAHAHAHAHA
Try again. |
Given that they can just turn the LEDs off to generate full black, I fail to see how they can't match the on/off ansi of CRT PJs. And the runco specs mention infinity:1 on/off - while having seemingly sane specs for other contrast levels. |
The LEDs dont turn off. They are still flashing even with a full black signal.
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macgyver655
Joined: 22 Aug 2007
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| Posted: Mon Apr 12, 2010 3:49 pm Post subject: |
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| emdawgz1 wrote: | | macgyver655 wrote: | | And if I were to say that even LED projectors are not capable of a true black......what would you say? |
I dunno.... It looked good to me..... |
The blacks are great. But they are still not true black but I didn't notice it either. Of course I'm also not that picky. A lot of things dont bother me in an image. I'm just throwing that point out there to have some fun.. 
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antorsae
Joined: 16 Jul 2006
Posts: 297
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| Posted: Tue Apr 13, 2010 8:51 am Post subject: |
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I did not know they cannot do zone-based dimming with LEDs PJs... I guess they would have to focus the light source in the chip/panel first and then refocus it on the screen... I do not know enough about optics to know if that's possible.
But anyway... they surpass CRTs in ANSI CR and full on/off I think they have POTENTIAL.
Let me put it this way: out of all the digital technologies available, this has the most potential and I will seriously consider this 2-3 yrs down the road when they mature. It's very nice what they have achieved in a first generation product (LED light sources are still in ther infancy). I think the Achilles heel is still brightness but again, LED sources still in their infancy and LEDs have the potential to scale better than Xenon or UHP lamps (I understand you can just stack more LEDs provided you have the right cooling).
I personally have a setup that I am not ready to trade-off until I get the best of both worlds (bright, convenience, uniformity, stability, plug and play of digitals and colors, dark scenes CRs, blacks, and motion of CRTs). It was a pain in the ass to have my setup ready (took literally years and me writing a custom blend software) etc. but there are some things a CRT can do that no digital can; and once you grow accustomed to them, it is difficult to switch (I've seen top of the line 3-chip PJs and I will not switch).
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