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I read this over at Keohi forum....you can see my question to the subject at hand...
http://www.keohi.com/ibf/hdtv/index....ST&f=33&t=2320
http://www.keohi.com/ibf/hdtv/index....ST&f=33&t=2320
LCDs self-destruct after 5 years?
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I never heard that one. I sincerely doubt it. Plasma is the technology that definitely degrades over time in terms of PQ until it is nothing but garbage, while replacing the bulb in a DLP makes it look like new. I always assumed LCD RPs would be similar to DLP, whereas flat panel LCDs would be similar to plasmas. Maybe that poster is confusing RP LCD with flat panel LCD? In either case, 5 years cannot be correct, at least with normal viewing habits.
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The new LCDs are good for 60k hours. That is 21 years based on 8 hours a day 365 days a year viewing.
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That's was my contention, Kipp. I know mfrs. will replace screens with several bad pixels in a cluster, etc. Those that are defective due to manufacturing defects. And those generally show up early on not later.
The good ones on a short term, generally end up lasting a very long time.
| Originally posted by Kipp Jones The new LCDs are good for 60k hours. That is 21 years based on 8 hours a day 365 days a year viewing. |
The good ones on a short term, generally end up lasting a very long time.
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Actually, LCD panels are like LCD RPs in that sense - if at any point the backlight will fail, it can be replaced like a lamp in a LCD RP that would make the panel look like a new one again. The difference is that end users are not able to perform this change on their own, it would require a professional service.
As for the pixels, for al lpractical reasons we can assume that the LCD panel will have only those dead/stuck sub-pixels that were found right after purchase. There is no reason to expect that the panel will develop new dead subpixels or any other visual artifacts (unless it is abused by users, like kids poking the panel with sharp objects).
| Originally posted by BillP ... I always assumed LCD RPs would be similar to DLP, whereas flat panel LCDs would be similar to plasmas. |
As for the pixels, for al lpractical reasons we can assume that the LCD panel will have only those dead/stuck sub-pixels that were found right after purchase. There is no reason to expect that the panel will develop new dead subpixels or any other visual artifacts (unless it is abused by users, like kids poking the panel with sharp objects).
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LCD's do age but for most viewers this would be 8 to 20 years before losing 50% brightness based on 8 hours a day of viewing. See below.
Display Aging
One topic that has turned into a hot marketing issue is display aging. While this is definitely a crucial issue for displays used in commercial applications that run continuously 24 hours per day (often with images that don't change much over time), it's really not a major issue for the current generation of displays in normal consumer use. However, the public's perception of the aging issue has been blown way out of proportion, particularly in the case of plasma displays, where many people are afraid to buy them for this very reason. None-the-less all displays do age so it's important to understand the issues and specifications involved. Displays age primarily based on the total accumulated hours of use. If you run a display an average of 4 hours per day that amounts to about 1,500 hours per year and 8 hours per day amounts to about 3,000 hours per year.
Phosphors are the source of light in CRT, LCD and plasma displays. The primary issue for these displays is phosphor aging. While you may hear talk about phosphor burn, the phosphors used in modern displays generally don't burn (which is actual heat damage to the phosphor that can be seen as a discoloration when the display is turned off). All phosphors lose brightness based on cumulative use, which results from Coulomb Aging (due to an electron beam current) or Solarization (due to ultraviolet radiation). The greater the electron current or ultraviolet radiation the faster the aging progresses. The aging specification is generally in hours of use up to when the brightness (luminance) falls to 50 percent of its original value, which is referred to as the Lifetime.
The backlight in LCDs is made up of a varying number of fluorescent lamps that have a phosphor coating. Most LCD displays have a Brightness Control that varies the brightness of the lamps, which affects the rate of aging and therefore the time to 50 percent luminance. You'll see a wide range of lifetime ratings for LCDs, typically from 25,000 to 60,000 hours. That should be 8 to 20 years of use at 8 hours per day before the brightness falls by 50 percent. However, there is a crucial yet subtle and often obscure or unreported factor in these lifetimes: it's the setting of the backlight intensity for the specified lifetime. Often it's not for the maximum backlight intensity, but rather for some lower value that ages more slowly, in which case the lifetime will be less and the display will age faster than you anticipate.
Be sure to find that out what brightness value the lifetime specification refers to. For LCDs the lamps should all age uniformly and, in principle, they can be replaced when they get too dim. Unless it's a really expensive display you probably won't find that worthwhile.
Display Aging
One topic that has turned into a hot marketing issue is display aging. While this is definitely a crucial issue for displays used in commercial applications that run continuously 24 hours per day (often with images that don't change much over time), it's really not a major issue for the current generation of displays in normal consumer use. However, the public's perception of the aging issue has been blown way out of proportion, particularly in the case of plasma displays, where many people are afraid to buy them for this very reason. None-the-less all displays do age so it's important to understand the issues and specifications involved. Displays age primarily based on the total accumulated hours of use. If you run a display an average of 4 hours per day that amounts to about 1,500 hours per year and 8 hours per day amounts to about 3,000 hours per year.
Phosphors are the source of light in CRT, LCD and plasma displays. The primary issue for these displays is phosphor aging. While you may hear talk about phosphor burn, the phosphors used in modern displays generally don't burn (which is actual heat damage to the phosphor that can be seen as a discoloration when the display is turned off). All phosphors lose brightness based on cumulative use, which results from Coulomb Aging (due to an electron beam current) or Solarization (due to ultraviolet radiation). The greater the electron current or ultraviolet radiation the faster the aging progresses. The aging specification is generally in hours of use up to when the brightness (luminance) falls to 50 percent of its original value, which is referred to as the Lifetime.
The backlight in LCDs is made up of a varying number of fluorescent lamps that have a phosphor coating. Most LCD displays have a Brightness Control that varies the brightness of the lamps, which affects the rate of aging and therefore the time to 50 percent luminance. You'll see a wide range of lifetime ratings for LCDs, typically from 25,000 to 60,000 hours. That should be 8 to 20 years of use at 8 hours per day before the brightness falls by 50 percent. However, there is a crucial yet subtle and often obscure or unreported factor in these lifetimes: it's the setting of the backlight intensity for the specified lifetime. Often it's not for the maximum backlight intensity, but rather for some lower value that ages more slowly, in which case the lifetime will be less and the display will age faster than you anticipate.
Be sure to find that out what brightness value the lifetime specification refers to. For LCDs the lamps should all age uniformly and, in principle, they can be replaced when they get too dim. Unless it's a really expensive display you probably won't find that worthwhile.
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if the title of this thread were true, sure hope you're keeping track by the year/month/day/hour/minute, and when it counts down to 00:00:00:00:00 be sure to duck behind the couch !!
kdog044,
"Phosphors are the source of light in ...... LCD...."
I do not believe this to be the case. As I recall individual liquid crystal modules are opened/closed in varying amounts (i.e. 256 levels) in front of, or back of, (- can't remember which side) red/blue/green filters (backlit with flourescent tubes) to create each RGB visually blended color pixel area in LCD displays - phosphors are not involved.
Perhaps someone can explain in detail if I'm wrong .... it's been awhile since I worked in the PC LCD driver electronics field!
"Phosphors are the source of light in ...... LCD...."
I do not believe this to be the case. As I recall individual liquid crystal modules are opened/closed in varying amounts (i.e. 256 levels) in front of, or back of, (- can't remember which side) red/blue/green filters (backlit with flourescent tubes) to create each RGB visually blended color pixel area in LCD displays - phosphors are not involved.
Perhaps someone can explain in detail if I'm wrong .... it's been awhile since I worked in the PC LCD driver electronics field!
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Quote:
I think they are referring to the backlight of LCD's. There are new technologies out there for LCD, such as Sony's Qualia (LED backlight) and Philips (hot cathode tube) but I believe most still use this type of backlight.
CCFTs (Cold Cathode Fluorescent Tubes) are used as the backlight source in most LCDs. The lifetime of a CCFT is defined as the time that it takes for the brightness to degrade to half the original brightness. Only a few years ago, the lifetime of a typical LCD CCFT was rated at 10 K hours. With changes in the gas mixture in the CCFT and the construction of the cathode it is now possible to realize lifetime of 50 K hours or longer. These are referred to as long life CCFTs.
| Originally posted by pnichols kdog044, "Phosphors are the source of light in ...... LCD...." I do not believe this to be the case. As I recall individual liquid crystal modules are opened/closed in varying amounts (i.e. 256 levels) in front of, or back of, (- can't remember which side) red/blue/green filters (backlit with flourescent tubes) to create each RGB visually blended color pixel area in LCD displays - phosphors are not involved. Perhaps someone can explain in detail if I'm wrong .... it's been awhile since I worked in the PC LCD driver electronics field! |
CCFTs (Cold Cathode Fluorescent Tubes) are used as the backlight source in most LCDs. The lifetime of a CCFT is defined as the time that it takes for the brightness to degrade to half the original brightness. Only a few years ago, the lifetime of a typical LCD CCFT was rated at 10 K hours. With changes in the gas mixture in the CCFT and the construction of the cathode it is now possible to realize lifetime of 50 K hours or longer. These are referred to as long life CCFTs.
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We had a thread going on the topic of projection (rear and forward) LCD panels that just ended 3 days ago.
http://www.avsforum.com/avs-vb/showt...hreadid=509123
Direct view LCDs are a different matter altogether.
http://www.avsforum.com/avs-vb/showt...hreadid=509123
Direct view LCDs are a different matter altogether.
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Accelerated aging tests are quite accurate for a variety of products if properly conceived. Temperature cycles, vibration, pressure (negative and positive), and shock/vibration as well as electrical stimulus, power cycling, can all be used in various schemes to closely simulate what devices would nomally be subjected to over an extended time.
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