[ITGuy72]

 http://1010wins.com/techbytes/local_...6165055.html/#

Quote:

A question I often get: which is better, plasma, or LCD for a new flat TV? Well. The LCD has been around longer, and its quirks have been worked out, but they tend to be expensive the bigger they get. Plasma TV's have many early adopters complaining of burn-in, where an image is left permanently on the screen, like a stock ticker or network ID. Also, plasma's can loose their sharpness and brightness over time, requiring service or replacement...

Would you guys aree with these statements? I was surprised to read plasma may loose sharpness over time.

 

[cxdmn2004]

 http://ne.nikkeibp.co.jp/members/NEW..._2IMG_0704.JPG

(picture is loading.....)

A real measurement chart of PDP vs LCD lifetime at SID2004


Latest generation PDP has longer lifetime than LCD.

 

[rogo]

If I am reading the chart right, the 60,000-hour-lifetime stats are actually way too low. At 60,000 hours, the PDP luminance would still be at roughly 300 cd/m2. That compares very favorably with "zero hour" luminance of 400 cd/m2 and "peak luminance" of 420 cd/m2.


It also looks like 3rd-generation PDPs -- what I'd assume are current models -- have licked the rapid-initial-decline in brightness problem. I suspect what used to happen is that something had some very initial early breakdown under the bombardment with UV or whatever wavelength was doing the damage. Some reformulation of the phopshor in the latest generation has "protected" against that breakdown.


An odd side effect is as the chemistry changes in the initial ownership period -- again all due to various kinds of EM emission, plasma gases are chemically inert -- the display actually gets brighter.


Note that the way the curve shown above is built, it has to be from actual-usage testing not unrelated approximations.


Not also that the 37" LCD must be the Sharp. I have one. I hope the CCFLs can be replaced at some time, because they sure as hell ain't going to be all that satisfying.


It is worth noting that data on CCFL (cold cathode fluorescent lamps, the stuff used to make LCD backlights) performance over long periods has not generallly been well studied with respect to peak luminance. Most laptops have never lasted long enough for it to matter.


I'm sure there is lab data at Sharp that refutes the above chart and says, "Hey, our lamps last way, way longer than you claim they do." But I think the important takeaway from the above is not that LCDs have lousy lifetime, but that current plasmas have lifetime that excceed any reasonable expecetations a consumer might place on them -- they are 20+ year displays, as we've been saying.


Now, that said, it's time to get answer on LCD backlight replacement possibilities and cost. It's also time to start getting some lifetime measurements on these things that are backed up by data. There are probably 24 backlights in my display. While the intrinsic cost of each lamp is on the order of $10, I doubt I could buy them for anything less than $50 each -- if at all. I also want to know whether the display should be babied a bit more. If it's really going to be noticeably dimmer after 5,000 hours, I'd try to get it into a bedroom sooner rather than later. It would be fine for many years in that environment as I can't imagine using a bedroom TV much more than 5 hours per week.


Mark

 

[genietime]

Mark,


Can you check into this? I find it almost impossible to believe that LCD panels decrease in brightness by over 25% in 7,500 hours. No way! I am of the impression that most manufacturers (LCD) claim 50,000/60,000 hours. I find it very odd that a CCFL would degrade that much.


As is true in all science, data must be able to be replicated. Let's see some other sources of data that say the same thing.

 

[rogo]

I am going to check into it, of course, as best I can.


That said, the LCD finding is -- to me -- a lot less relevant than the plasma finding. They doubtless bought one model of LCD -- perhaps a couple of panels -- to do what they did. By contrast, whoever's study this was is obviously a plasma maker. They are kind of beholden to what they are saying about plasma.


Mark

 

[Picus_H]

I've never heard of a plasma or LCD losing sharpness over time. I won't comment on the brightness aspect as that been beaten to death - but I think that without any evidence (of which we have none) I'd venture to guess that the sharpness thing is probably not true or, if it is, not really relevant (since it might mean at 100,000 hours, or a sharpness difference that can't be seen). The 5UYs I have are just as sharp and clear at 17,111 hours to the nakes eye as the 6UYs at 1,111 right beside them.

 

[rogo]

There isn't even any technical reason for either display type to lose sharpness.

 

[Bishamon]

Looks to me like a comparison of LCD projection versus plasma, since current generation LCD panels have a 60,000hr+ rating with near 90% brightness until just before 'the end'.

 

[bruce banner]

Do I have a second generation plasma? It a TH-42PWD5UY.

 

[wojtek]

Quote:

Originally posted by Bishamon Looks to me like a comparison of LCD projection versus plasma, since current generation LCD panels have a 60,000hr+ rating with near 90% brightness until just before 'the end'.

37" diagonal is either a very big LCD projection chip or a very small LCD projected image

 

[rogo]

Yeah, Bishamon, that's clearly not what it is.


It's also just not true that CCFL's maintain brightness at the 90% level and then just go dark after 60,000 hours. They do lose more brightness than that over time. The question is: How much?


Another concern I've had with my LCD and with the technology in general at large sizes is that there are alread two-dozen backlights in the 30-32' range. There will be something like 50 on a 46" set. They will not likely lose brightness in anything resembling a fully uniform fashion. I wonder what that means to luminance uniformity over time.


Mark

 

[slb]

Quote:

Do I have a second generation plasma? It a TH-42PWD5UY.

Although we don't know for sure who generated the data, my guess would be that the 5-Series Pannys fall into the 3rd gen category. One would need to have started collecting data over 4 years ago (assuming 24hrs/day of operation) to generate that data. Even the 4-Series Pannys fall into that time window.


-Steve


Edited for clarity

 

[PanamaMike]

LCD is always improving by leaps and bounds, however I can only state what I've seen.


I've been aound LCD technology for the past 10 years. It's definately gotten better, but the one thing that surprised me was how quickly the display quality degraded.


If you take a look at a professionals laptop screen, you can definately tell the LCD panel looks dim or "burned out". The first time I saw this, I literally thougth the screen was dirty. I couldn't believe how badly the screen looked.


That was about 3 years of use at what I suspect to be 9 to 10 hrs a day. It was a friend of mines consultant laptop. The first time I saw this was about 3 years ago. I've seen screens that look like this about 4 or 5 times. Now I'm watching to see how long my personal laptop screen lasts

 

[Bishamon]

Quote:

Originally posted by rogo Yeah, Bishamon, that's clearly not what it is.

Then I would definitely question the validity of the study, since LCD backlights clearly last more than 7500 hours. Unless whatever 37" display they were testing (Sharp, I would assume) has a rediculously short backlight lifespan (or it had something wrong with it).

Quote:

It's also just not true that CCFL's maintain brightness at the 90% level and then just go dark after 60,000 hours. They do lose more brightness than that over time. The question is: How much?

I was only quoting what I have been told by various manufacturers. Of course, similar claims as to sustained brightness levels have also been made for LCD and DLP projection bulbs, though with a much shorter lifespan.

Quote:

Another concern I've had with my LCD and with the technology in general at large sizes is that there are alread two-dozen backlights in the 30-32' range. There will be something like 50 on a 46" set. They will not likely lose brightness in anything resembling a fully uniform fashion. I wonder what that means to luminance uniformity over time.

Good question. Also, as more backlights are added, the heat generated increases (not to mention power consumption), negating one of the 'benefits' of LCD technology. My 32" Sammy definitely generates a lot of heat, and I can only imagine the 40" must run much warmer.


There is actually a 17" Samsung LCD at a local Future Shop that has a horizontal dark band which appears to be a row of backlights (or a single backlight?) that is non-fuctional.

 

[bruce banner]

Quote:

Originally posted by slb Although we don't know for sure who generated the data, my guess would be that the 5-Series Pannys fall into the 3rd gen category. If the graph represents actual data (and it appears so), 35000 hrs is equivalent to 4 years at 24hrs/day operation. Even the 4-Series Pannys fall into that time window. -Steve

Oh, okay.

 

[rogo]

Bishamon, if you read my original post above closely, you'll see I too am questioning the results on the LCD. It's clear that the study was done by someone with access to a ton of PDPs and one particular LCD, where they might've had 2-4 displays, tops.


You wrote: "I was only quoting what I have been told by various manufacturers. Of course, similar claims as to sustained brightness levels have also been made for LCD and DLP projection bulbs, though with a much shorter lifespan."


And we know it's just a lie about projector bulbs. They are nowhere near as good as 90% before burnout.


You wrote: "Good question. Also, as more backlights are added, the heat generated increases (not to mention power consumption), negating one of the 'benefits' of LCD technology. My 32" Sammy definitely generates a lot of heat, and I can only imagine the 40" must run much warmer."


Yes, I still think there is a power edge for LCD, but it's smaller as sizes get bigger. We must learn more.

 

[RayL Jr.]

Well, taken from NEC cold cathode fluorescent lamps:

http://www.nelt.co.jp/nhe_hp/cfl/rk_tj_ki.jpg


NEC lamps rated for 50,000 hours, it looks like it does drop off more rapid for conventional CCFLs. More reason I'm waiting for LED backlighting later this year (Luxeon LED backlit displays), LEDs can to go up to 100,000 hours! From Lumled's site they might be 90% after 10,000 hours.


Here's Lumiled press releases and NEC press releases pages .

 

[Bishamon]

Quote:

Originally posted by rogo You wrote: "I was only quoting what I have been told by various manufacturers. Of course, similar claims as to sustained brightness levels have also been made for LCD and DLP projection bulbs, though with a much shorter lifespan." And we know it's just a lie about projector bulbs. They are nowhere near as good as 90% before burnout.

That's what I was getting at, actually.


It seems to be very difficult to find accurate comparative information on LCD and PDP longevity; most of the reports are either one sided, depending on what the manufacturer wants to sell that quarter; or chock full of false information. It's no wonder consumers have no idea what's going on when the media really has no idea, and vendors either have no idea or are emphasizing certain advantages and disadvantages to suit their own goals.

 

[xrox]

Quote:

Originally posted by rogo Yes, I still think there is a power edge for LCD, but it's smaller as sizes get bigger. We must learn more.

I've just read recently that the power consumption of plasma screens increase as pixel size decreases. So in essence the smaller you make a plasma screen the more power/pixel it will consume. Seems the opposite of LCD


Although this seems irrelevant, when applied to the problem of making a higher resolution plasma the same theory applies (because you must make smaller pixels).


Plasma display pixels (cells) are fundamentally no different than a flourescent light bulb (in LCD). Except that a flourescent light bulb is larger which allows for greater efficiency (~80lm/Watt). As you make the cell smaller the efficiency goes down and power consumption goes up


If you wish to know why? Well here is what was written in the article (tried to eliminate jargon as best I could )

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

All gas discharge cells have two luminous regions, the positive column and the negative glow. The positive column is magnitudes more efficient than the negative glow. The larger the cell the larger the positive column relative to the negative glow, hence the better the efficiency. As you make the cell smaller the negative glow component becomes larger relative to the positive column and thus lowers the efficiency and raises power consumption.

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


All is not lost though. Matsushita Plasmaco has already designed a high efficiency positive column 42 screen


Cheers

 

[rogo]

RayL: Thanks. Awesome stuff. I'm still concerned about how uniform those declines are. I wonder if the Sharp that was apparently used in the test has some oddball CCFLs to produce extra light because the display is so darned big. Perhaps those are not that long lasting?


Bishamon: I tend to disregard what the guys say about the competition, they aren't held accountable for that. But the real results of that study are clear: Plasma longevity is simply not a real issue. The chance for burn-in remains an issue, but longevity isn't one.


For LCD, the longevity issue is also secure. The question for me now is: How real is the risk of non-uniform brightness declines? What is CCFL life really? 20,000 hours till 50%? 50,000 hours till 50%? It is clear that the CCFL's lose brightness over time. How much and how soon and how consistently are real issues?


All: Over time LED backlights might become real. They are more expensive right now and the need is not entirely compelling. There is some inevitability to OLEDs taking over for TFT-LCDs anyway as I think ultimately OLEDs will be appreciably cheaper to build. But given that we are a decade from the end of TFT-LCD -- at least -- whether LED backlights will become ubiquitous remains to be seen.