Who cares about 4K? I want local dimming based projectors! - AVS Forum
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Digital Hi-End Projectors - $3,000+ USD MSRP > Who cares about 4K? I want local dimming based projectors!
opv's Avatar opv 02:53 AM 02-11-2013
I had a thought, what is the bottle neck in today's digital projectors image quality.
Is it really resolution? I don't think so. 1080P resolution is sufficient unless you take the screen size to viewing distance ratio to extreme levels.
The real bottle neck, is still contrast. Static contrast and to be more specific, ansi contrast.
Flat panel displays have reached ansi contrast numbers that are equivalent to static on off contrast ratio of projectors.
How did the LCD flat panel technology, overcome the contrast limits of the LCD panel? They added local dimming light source that acts as a second light modulator.
We know of double light modulation projectors that reach huge contrast ratios but suffer from low light efficiency, not to mention the price.
If we take the double light modulation concept, but use a led matrix light source as the first light modulator we can greatly improve the light efficiency.
Apparently, I'm not the only one thinking in this direction; I found a patent by Dolby for local dimming of a laser light source for projectors:
http://patentscope.wipo.int/search/en/detail.jsf?docId=WO2012125756&recNum=1&tab=PCTDocuments&maxRec=&office=&prevFilter=&sortOption=&queryString=

So, what do you think, is this a technology that will affect HT projectors?
Or will it remain an option for planetarium projectors, like the current double modulation projectors

Seegs108's Avatar Seegs108 02:58 AM 02-11-2013
Quote:
Originally Posted by opv View Post

I had a thought, what is the bottle neck in today's digital projectors image quality.
Is it really resolution? I don't think so. 1080P resolution is sufficient unless you take the screen size to viewing distance ratio to extreme levels.
The real bottle neck, is still contrast. Static contrast and to be more specific, ansi contrast.
Flat panel displays have reached ansi contrast numbers that are equivalent to static on off contrast ratio of projectors.
How did the LCD flat panel technology, overcome the contrast limits of the LCD panel? They added local dimming light source that acts as a second light modulator.
We know of double light modulation projectors that reach huge contrast ratios but suffer from low light efficiency, not to mention the price.
If we take the double light modulation concept, but use a led matrix light source as the first light modulator we can greatly improve the light efficiency.
Apparently, I'm not the only one thinking in this direction; I found a patent by Dolby for local dimming of a laser light source for projectors:
http://patentscope.wipo.int/search/en/detail.jsf?docId=WO2012125756&recNum=1&tab=PCTDocuments&maxRec=&office=&prevFilter=&sortOption=&queryString=

So, what do you think, is this a technology that will affect HT projectors?
Or will it remain an option for planetarium projectors, like the current double modulation projectors

Just some food for thought; Panasonic's VT50 panels only have on/off numbers of ~11000:1 and the black levels on almost all of todays home theater projectors can reach a lower black level. That isn't particularly high and that is one of the best panels in regards to on/off. The Kuro's obviously are better but they aren't being produced anymore, unfortunately.

As far as ANSI contrast goes, HDTVs are totally different compared to projectors. The slightest amount of ambient light hitting your screen kills ANSI contrast. You simply don't have that issue with flat panel displays. I don't think that is something projectors can really improve upon. The best you're going to see, as long as you have an appropriate room, is ~900:1 from a projector. My LED projector is right around that number with on/off ~22000:1 with the LED dimming set to it's medium aggressive mode. I think as far as contrast and black levels it blows most HDTVs out of the water.
opv's Avatar opv 03:04 AM 02-11-2013
Seegs108,
Why the fact that the Kuro isn't available anymore does makes any difference?
CRT projectors are also long gone but I still strive to the same black levels from a digital projector.
We're talking about measured ansi contrast ratio of 3000+ for the Kuro and the Toshiba ZL1 vs. a very optimistic ratio of 800 for some DLP projectors. That's one big difference...
Andreas21's Avatar Andreas21 03:08 AM 02-11-2013
Panasonic 65VT50 is measured by AVForums in England to have on/off at 11778:1 and ANSI contrast at 4778:1(I think the ANSI number is to high around 3000:1 is more correct I think). ANSI numbers are impressive but on/off not that imperessive, I have the Panasonic 65VT30 and I think it measures about the same and I have a VW1000 in my cinema and I find the VW1000 to have the best picture by far!smile.gif

So ANSI contrast alone does not make a good picture.
opv's Avatar opv 03:17 AM 02-11-2013
Andreas21,
I believe that On/Off contrast has much more effect on picture quality than anything else.
But you don't have to sacrifice on/off contrast to improve ansi contrast.
I believe that a VW2000 with the same on/off ratio and twice the ansi ratio, will be better than the VW1000, don't you?wink.gif
Seegs108's Avatar Seegs108 03:22 AM 02-11-2013
Yes, but you're asking for the impossible. Projectors (and more specifically the room and the screen being used) can't reach numbers that high and you can't expect them to. There will always be too much light scattering across the screen and light reflecting back on the screen for numbers higher than what we are currently seeing with the current projection technology being used. So unless there is some breakthrough with screen technology (or possibly projector technology) don't expect those numbers to go over 1000:1 any time soon.
opv's Avatar opv 03:27 AM 02-11-2013
Seegs108,
I'm not talking about living room conditions, but bat cave conditions with black seats and viewers dressed as Ninjas.
Assuming these conditions, Are you sure that the room and screen are the limiting factors?
Seegs108's Avatar Seegs108 03:28 AM 02-11-2013
Quote:
Originally Posted by opv View Post

Seegs108,
I'm not talking about living room conditions, but bat cave conditions with black seats and viewers dressed as Ninjas.
Assuming these conditions, Are you sure that the room and screen are the limiting factor?

Yes. Without a doubt. Stray and reflecting light on the screen is ANSI contrast's worst enemy as far as projectors go. Even in batcave situations you have this and ANSI suffers.
opv's Avatar opv 03:33 AM 02-11-2013
Seegs108,
I haven't tested the subject, so I'll take your word for it.
But why do we focus only on ansi contrast?
The static on/off contrast can also be improved using this method.
Getting great CR ratios using a DI and static or semi static CR don't have the same effect on picture quality.
Seegs108's Avatar Seegs108 03:37 AM 02-11-2013
I'm not saying ANSI contrast should be focused on. Just look at JVC projectors. They typically measure only ~300:1 (some models a little higher) and look great. Overall On/Off numbers can have a bigger effect on how contrast appears. High ANSI contrast does have it's benefits though. A projector with very high ANSI contrast can appear to have blacker blacks in all but the darkest scenes compared to something like a JVC. This is true for good DLP projectors.
Seegs108's Avatar Seegs108 03:51 AM 02-11-2013
As long as you're taking these measurements in a batcave like room, On/Off numbers aren't effected anywhere near as much as ANSI contrast is. Think about it. At peak white you want as much light hitting the screen to get a high number. When the screen is fully black there will be a minimal amount of light scattering on the screen and an even smaller amount reflecting on the screen. You get the best scenarios for each measurement. When you take ANSI contrast measurements you have tons of light from the white squares that is scattering and reflecting on the black ones. You need exceptional optics and an amazing room to get decent ANSI contrast measurements. This is typically why more expensive projectors measure higher in ANSI contrast. They typically have much better optics which can greatly reduce light scatter inside the lens/projector and on your screen.
opv's Avatar opv 04:46 AM 02-11-2013
I totally agree that on/off contrast is more important than ansi contrast.
But even the on/off contrast ratios of projectors aren't high enough.
Take your pick of any digital projector (not including the two double modulation projectors), and put a black screen in a black cave. The room will not be totally dark you'll be able to see the screen and you'll see the people sitting next to you.
That should be a very simple scenario, but even with the use of DI you still can't get perfect blacks.
With light source dimming, you can get these black levels, theoretically.
Sona Kakoo's Avatar Sona Kakoo 06:53 AM 02-11-2013
Quote:
Originally Posted by Seegs108 View Post


As far as ANSI contrast goes, HDTVs are totally different compared to projectors. The slightest amount of ambient light hitting your screen kills ANSI contrast. You simply don't have that issue with flat panel displays. .

plasma with ambient light are worst (black/contrast) than any old lcd (and killed by good ones).

Quote:
My LED projector is right around that number with on/off ~22000:1 with the LED dimming set to it's medium aggressive mode. I think as far as contrast and black levels it blows most HDTVs out of the water

i don't think it can reach best lcd or plasma levels, or please, tell me what kind of new laser projector are you using ? smile.gif (the best one i've seen, acer k750, is clearly inferior to the best actual projector X35 , hw50, etc who don't beat easilly best flat tv for contrast/blacks)
Andreas21's Avatar Andreas21 08:14 AM 02-11-2013
Quote:
Originally Posted by opv View Post

Andreas21,
I believe that On/Off contrast has much more effect on picture quality than anything else.
But you don't have to sacrifice on/off contrast to improve ansi contrast.
I believe that a VW2000 with the same on/off ratio and twice the ansi ratio, will be better than the VW1000, don't you?wink.gif

Of corse!smile.gif

But I don´t think we will se those ANSI numbers in any projectors any time soon and you need to hava a very special room to make it happen...
Seegs108's Avatar Seegs108 02:54 PM 02-11-2013
Quote:
Originally Posted by Sona Kakoo View Post

plasma with ambient light are worst (black/contrast) than any old lcd (and killed by good ones).



i don't think it can reach best lcd or plasma levels, or please, tell me what kind of new laser projector are you using ? smile.gif (the best one i've seen, acer k750, is clearly inferior to the best actual projector X35 , hw50, etc who don't beat easilly best flat tv for contrast/blacks)

They aren't going to reach the same level as the best LCD/Plasma TVs and people shouldn't expect them to. There a very few reviews of the Acer K750. From what it looks like, it seems that it's totally different from my LED projector. It's going to use a cheap lens, a smaller DMD, and from what I've read doesn't seem to achieve that great of a black level. The cheap lens and smaller DMD will greatly effect the ANSI contrast ratio. Like I said, my LED projector has a measured ~900:1 and 22000:1 on/off. The combination of high ANSI and high on/off gives you better intra-scene contrast compared to the X35 and the HW50. Only the darkest scenes like star fields will have higer intra-scene contrast compared to the x35. With any other content it blows the X35 out of the water.

Quote:
Originally Posted by opv View Post

I totally agree that on/off contrast is more important than ansi contrast.
But even the on/off contrast ratios of projectors aren't high enough.
Take your pick of any digital projector (not including the two double modulation projectors), and put a black screen in a black cave. The room will not be totally dark you'll be able to see the screen and you'll see the people sitting next to you.
That should be a very simple scenario, but even with the use of DI you still can't get perfect blacks.
With light source dimming, you can get these black levels, theoretically.

This isn't entirely true. My LED projector has a DI, but it's not a DI in the traditional sense. It is exactly what you're talking about. It's light source dimming. The LEDs themselves dim to fit the scene. There is a setting that allows for them to basically shut off when there is nothing but black on the screen. There are issues when using this mode. It is far too aggressive to use for practical means. There will be too much brightness pumping for this mode to be used during normal viewing. Sure this mode is great for test purposes but you aren't going to use it in practice.
dougri's Avatar dougri 03:50 PM 02-11-2013
Quote:
Originally Posted by Seegs108 View Post

They aren't going to reach the same level as the best LCD/Plasma TVs and people shouldn't expect them to. There a very few reviews of the Acer K750. From what it looks like, it seems that it's totally different from my LED projector. It's going to use a cheap lens, a smaller DMD, and from what I've read doesn't seem to achieve that great of a black level. The cheap lens and smaller DMD will greatly effect the ANSI contrast ratio. Like I said, my LED projector has a measured ~900:1 and 22000:1 on/off. The combination of high ANSI and high on/off gives you better intra-scene contrast compared to the X35 and the HW50. Only the darkest scenes like star fields will have higer intra-scene contrast compared to the x35. With any other content it blows the X35 out of the water.
This isn't entirely true. My LED projector has a DI, but it's not a DI in the traditional sense. It is exactly what you're talking about. It's light source dimming. The LEDs themselves dim to fit the scene. There is a setting that allows for them to basically shut off when there is nothing but black on the screen. There are issues when using this mode. It is far too aggressive to use for practical means. There will be too much brightness pumping for this mode to be used during normal viewing. Sure this mode is great for test purposes but you aren't going to use it in practice.

Light source dimming on the a PJ is like the 'dynamic contrast' setting on LED HDTVs... dimming the backlight. The original question dealt with local dimming... which is pretty similar to how a DLP operates anyway (only it diverts the light instead)... just has some efficiency problems with light scattered of the micromirror edges, the DMD sub-structure, and bouncing around the lens (especially the off-state light). The amount of light scattered with .95" DMDs and good optics is very low (as is evidenced by Seeg's numbers)... the reason for moving to smaller DMD was cost (optics and DMD, but needed a higher quality lens even if smaller to get the same performance). Would it make sense to go the other way (produce a larger DMD, not that TI would do that) with laser light source since it allows for smaller lens? The smaller lens would further separate off/on states and the large micromirrors would increase SNR?
noah katz's Avatar noah katz 08:53 PM 02-11-2013
I think the problem in applying local dimming to pj's is size; doing it with hundreds of square inches of flat panel is one thing; doing it with a fraction of a sqaure inch of pj display chip is a much bigger challenge.
DLPProjectorfan's Avatar DLPProjectorfan 09:08 PM 02-11-2013
Who cares about 4 K resolution ?

The real question that should be asked is ? who can afford it.

The average man or woman can not afford it in this economy unless your wealthy and well off.

However you are correct, 1080P is sufficient for most people.

For most people it's not a matter if they want it it's a matter of can they afford it and where their priorities are.
Seegs108's Avatar Seegs108 09:13 PM 02-11-2013
Quote:
Originally Posted by DLPProjectorfan View Post

Who cares about 4 K resolution ?

The real question that should be asked is ? who can afford it.

The average man or woman can not afford it in this economy unless your wealthy and well off.

However you are correct, 1080P is sufficient for most people.

For most people it's not a matter if they want it it's a matter of can they afford it and where their priorities are.

The same thing has been said about any new form of display technology. Though, 4K will be a little different. Most people aren't going to have the correct size screen to actually get the full benefit of 4K resolution. You're going to need to have a screen that's at least 10 feet wide to get the full benefit of 4K.

As far as local dimming goes, it's going to be close to impossible to get something like this implemented considering the size of the panels/DMDs.
mark haflich's Avatar mark haflich 12:05 AM 02-12-2013
I think it could be accomplished but I am not sure.

Two possibilities come to mind. The right lind of lazer illuminted projector or by placing a panel in front of, could be transmissive or reflective, in fromt of the colated three panels. One would a localized dimming, the other would be a per pixel iris accomplishing the same thing. I dunno, just some ideas.

Re the cost of large panel 4K, the cost will drastically decrease in a few years just like large 1080p panels.

4K will provide a lot more than increased pixel desity which I agree a large screen is required for full appreciation. Not so for FPs and largescreens. Simply put it wil come with a much wider color space, double under the UN ITU standard and a longer bit length needed to get rind of banding cause by 8 bit length and the crappy solutions like dither noise presently being used to mask it. I am sure I haven't got this right but you can get the general idea. Moreover , we will get a huge increase in the number of colors even without an expansion of the color space. Plus we will have 4K souces. More actual data.

this will happen because the manufacturers know that 4k won't be adopted by the market with these other things because Joe Market won't have a large enough screen..

Cost factors go away. When the first color sets came out, they were very expensive in those year's dollars. Many who really wanted it but couldn't afford it had to build it from a Heath Kit,


Now you cam't buy a black and white set and all programming except for someold movies, etc which were shot in black and white.
opv's Avatar opv 02:31 AM 02-12-2013
Quote:
Originally Posted by noah katz View Post

I think the problem in applying local dimming to pj's is size; doing it with hundreds of square inches of flat panel is one thing; doing it with a fraction of a sqaure inch of pj display chip is a much bigger challenge.
Noah,
The number of areas in the local dimming light source can be much smaller than the panel resolution.
I think that a local dimming source with, say 16 areas, will give a great improvement comparing with today's "one area local dimming" the DI.
Do you think a 16 led matrix as a light source for a projector, is still not feasible?

By the way, another option for implementing local dimming light source is to use a low resolution scanning light source, like laser or something like a low resolution CRT tube.
tvted's Avatar tvted 03:54 AM 02-12-2013
The possibility of local area contrast control has been discussed in the past when the idea of adding of adding a fourth panel was suggested (DarinP?).
Seegs108's Avatar Seegs108 03:56 AM 02-12-2013
Quote:
Originally Posted by opv View Post

Noah,
The number of areas in the local dimming light source can be much smaller than the panel resolution.
I think that a local dimming source with, say 16 areas, will give a great improvement comparing with today's "one area local dimming" the DI.
Do you think a 16 led matrix as a light source for a projector, is still not feasible?

By the way, another option for implementing local dimming light source is to use a low resolution scanning light source, like laser or something like a low resolution CRT tube.

I think the better question to ask is how small can they be? You'd have to use fiber optics or something to directionalize the light. This is what Mark was talking about with lasers. It would seem they are the more logical choice here.
opv's Avatar opv 03:58 AM 02-12-2013
Quote:
Originally Posted by tvted View Post

The possibility of local area contrast control has been discussed in the past when the idea of adding of adding a fourth panel was suggested (DarinP?).
Yes,
I mentioned that option of double light modulation in the beginning of the thread.
Double light modulation does indeed improve static contrast dramatically .
The problem is very low light efficiency.
Using a light source as the second modulator, solves the light efficiency issue.
tvted's Avatar tvted 09:16 AM 02-12-2013
Quote:
How did the LCD flat panel technology, overcome the contrast limits of the LCD panel? They added local dimming light source that acts as a second light modulator.
We know of double light modulation projectors that reach huge contrast ratios but suffer from low light efficiency, not to mention the price.

I'm not convinced that the above indicates that you were referring to an additional chip transmissive chip soley for the purpose of light modulation but ok.
Quote:
Double light modulation does indeed improve static contrast dramatically .
The problem is very low light efficiency.
What is the lumens loss in adding transmissive chip to an optical block?

I've not read the patent document you referred to but if you have what is the estimated matrix proposed? I do not consider a granularity of 16 worth the effort frankly.
opv's Avatar opv 09:27 AM 02-12-2013
tvted,
From what I remember from the threads dealing with double light modulation projectors, the light loss is huge, something like 80%.

I gave the 16 area matrix as an example, but yes, I think such a matrix is worth the effort.

Regarding the patent, I didn't have a chance to dive into the details yet.
space2001's Avatar space2001 09:33 AM 02-12-2013
The Big next step is laser scanning. Unfortunately Right now the tech is not there to do 1080p, since the scan is not fast enough, but who knows if that will change.
opv's Avatar opv 10:15 AM 02-12-2013
Quote:
Originally Posted by space2001 View Post

The Big next step is laser scanning. Unfortunately Right now the tech is not there to do 1080p, since the scan is not fast enough, but who knows if that will change.
You can use low resolution light scanning as a first modulator and one of the existing technologies like LCD DLP or LCOS as the main modulator.
This way you overcome the scanning resolution limit.
dougri's Avatar dougri 12:35 PM 02-12-2013
Quote:
Originally Posted by opv View Post

You can use low resolution light scanning as a first modulator and one of the existing technologies like LCD DLP or LCOS as the main modulator.
This way you overcome the scanning resolution limit.

In theory... I think the result would be less than anticipated though. I do most of my TV viewing on an LG 55LHX... fantastic picture, backlit led local dimming with 240 zones. Even though the 55LHX has an excellent implementation of zones, I find the zones to be clearly visible if I stand closer than ~8ft (viewing dist of 2 screen widths) due to spill into areas intended to be dark. Now, those zones are ~5.4sqin. So, I would consider 240 zones to be too few for projection with typical viewing distance between 1-1.8 screen widths. And that is best case. Lets assume that the same 8ft viewing of 5.4 sqin zones is 'acceptable'. Now consider 1x viewing distance with an 8ft wide screen and the same 8ft viewing distance... Now we're over 900 zones. Sure, a lot less than 2M, but not just a few. Might be doable. Me? I'm hoping RGB laser DLP works its way into the consumer marketplace.
mark haflich's Avatar mark haflich 12:42 PM 02-12-2013
None of this is going to happen in the foreseeable future. Its not like large masses purchase projectors and those that do don't say take it back, the black's suck. In commercial theaters nobody bitches about the blacks and those that have such an animal for their house just order it up with a special iris plate to cut down the light while improving the blacks. It simply is not going to happen. So be happy that 4K will come with its resolution not related other improvements.
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