LCD vs. LED - Light Output over time? - AVS Forum
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Old 12-21-2009, 01:17 PM - Thread Starter
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I've done some research around LED vs. LCD (bulb as the source of light) televisions but still struggle with understanding one aspect. With LCD there is normally a very bright image at first but over time lumen ouput should decrease and eventually become somewhat dim. When this happens you can easily buy a new bulb and have close to a new television experience again and go through the same process. I assume with LED you really don't have this option since it would be cost prohibitive to replace the entire LED.

So how does LED perform over time when compared to LCD? Does LED go through a similar pattern of dimming over time and if so what would the differences be?
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Old 12-21-2009, 02:20 PM
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I think that you can expect 11 years from LED LCD. By the time you would need to have the LEDs replaced you may actually be able to get 52 inch OLED.
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Old 12-21-2009, 03:14 PM - Thread Starter
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Originally Posted by spyboy View Post

I think that you can expect 11 years from LED LCD. By the time you would need to have the LEDs replaced you may actually be able to get 52 inch OLED.

Thanks for that. However, what I'm curious about is how the light output degrades over time. Here is a real world example.

I use a Sanyo PLV70 in a dedicated home theater I have. I find that after I put in a new bulb I get exceptional brightness for the first 200 hours or so. After that it slowly starts to dim. By 1500 hours is pretty dim and probably warrants being replaced.

So eventhough that is a projector the analogy is somewhat the same with LCD TV's. What I'm curious about is how does LED work in this respect. Is it similar? If it has 11 years of life can you expect the 1st year to display optimal brightness and then degrade? OR does it perhaps use superior technology when compared to LCD Bulbs and truly doesn't degrade light output at all for 11 years?
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Old 12-21-2009, 03:28 PM
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Originally Posted by JP View Post

I've done some research around LED vs. LCD (bulb as the source of light) televisions but still struggle with understanding one aspect. With LCD there is normally a very bright image at first but over time lumen ouput should decrease and eventually become somewhat dim. When this happens you can easily buy a new bulb and have close to a new television experience again and go through the same process.

Why not just turn the back light up a notch IF this happens? The first thing you do with an LCD when you take it out of the box is turn off torch store demo mode.
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Old 12-21-2009, 07:29 PM - Thread Starter
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Originally Posted by Ranger 518 View Post

Why not just turn the back light up a notch IF this happens? The first thing you do with an LCD when you take it out of the box is turn off torch store demo mode.

Because this is likely to make the image worse, not better. Having your light source dim can't be easily rectified by just adjusting something like gamma, contrast, or brightness. I wish you could. Naturally, you would want to calibrate any display out of the box and I suspect calibrating it later might help temper the issue I'm describing a bit but ultimately, it would be best to replace the light source like so many do with a bulb when the dimming becomes pronounced.
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Old 12-21-2009, 07:45 PM
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JP,
Since there are no longer any LED based DLP RPTVs being manufactured I think you should look fior somethng else then a used Samsung LED based DLP RPTV,
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Old 12-21-2009, 07:48 PM - Thread Starter
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Originally Posted by walford View Post

JP,
Since there are no longer any LED based DLP RPTVs being manufactured I think you shouoed look fior somethng else then a used Szmxung LED based DLP RPTV,

Any suggestions?
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Old 12-22-2009, 08:04 AM
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My personnel preference would be for a Local Dimming LED backlit LCD flat panel.
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Old 12-22-2009, 09:02 AM
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Quote:
Originally Posted by JP View Post

I've done some research around LED vs. LCD (bulb as the source of light) televisions but still struggle with understanding one aspect. With LCD there is normally a very bright image at first but over time lumen ouput should decrease and eventually become somewhat dim. When this happens you can easily buy a new bulb and have close to a new television experience again and go through the same process. I assume with LED you really don't have this option since it would be cost prohibitive to replace the entire LED.

So how does LED perform over time when compared to LCD? Does LED go through a similar pattern of dimming over time and if so what would the differences be?

LCDs are LCDs no matter how they are lit.

The two current methods are CCFL LCD or LED LCD. It's a bit frustrating that many folks always refer to them as EITHER LCD or LED. Even if they know the difference, many non-technical folks on this Forum won't and may get the wrong idea. LED is not always better. I'd rather have a Samsung B760 that's CCFL back-lit than a Samsung B6000 that's LED edge-lit. The lighting on the B750 is more uniform and less prone to flashlighting and clouding than the B6000, no matter how sexy the B6000 looks when it's not turned on.

As for how long each will last, I don't think the average person will ever have to worry about a TV with a 60,000 hour minimum life. Even with a half-life of 30,000 hours before you may begin to notice a slight difference in the brightness, that would give you over 10 years of viewing even if you watched it 8 hours a day every day of the year.
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Old 12-22-2009, 11:26 AM
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Quote:
Originally Posted by walford View Post

My personnel preference would be for a Local Dimming LED backlit LCD flat panel.

Why? If you take the top rated CCFL and the top rated edge lit LED and the top rated local dimming LED how would they compare? Do the advantages become more evident as the panel size increases? The value of course would be up to the individual but what kind of price differences can be expected with the three technologies? I would bet that most buyers in the 52"-55" range are asking themselves these questions.
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Old 12-22-2009, 12:35 PM
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Quote:
Originally Posted by BoilerJim View Post

As for how long each will last, I don't think the average person will ever have to worry about a TV with a 60,000 hour minimum life.

Doesn't sound like JP is the average person. HE WANTS TO KNOW!

Sumbody said a CCFL dims to about 90% of max after 1 year, then stays there until the end of life. UNCONFIRMED.

Edge-lit LED should be not too hard or expensive to replace, but again, I haven't done one so can't guarantee that's the case.
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Old 12-22-2009, 12:41 PM
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Quote:
Originally Posted by andy sullivan View Post

Why? If you take the top rated CCFL and the top rated edge lit LED and the top rated local dimming LED how would they compare? Do the advantages become more evident as the panel size increases? The value of course would be up to the individual but what kind of price differences can be expected with the three technologies? I would bet that most buyers in the 52"-55" range are asking themselves these questions.

maybe I'm biased (8500 owner) but the reviews all show that local dimming sets are the clear winner. Turning off the local dimming feature of my set shows a clear drop in picture quality. From what I could tell, ccfl vs edge lit led isn't as obvious who the winner is, but most say ccfl is better.
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Old 12-22-2009, 01:20 PM
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Quote:
Originally Posted by JP View Post

Thanks for that. However, what I'm curious about is how the light output degrades over time. Here is a real world example.

I use a Sanyo PLV70 in a dedicated home theater I have. I find that after I put in a new bulb I get exceptional brightness for the first 200 hours or so. After that it slowly starts to dim. By 1500 hours is pretty dim and probably warrants being replaced.

So eventhough that is a projector the analogy is somewhat the same with LCD TV's. What I'm curious about is how does LED work in this respect. Is it similar? If it has 11 years of life can you expect the 1st year to display optimal brightness and then degrade? OR does it perhaps use superior technology when compared to LCD Bulbs and truly doesn't degrade light output at all for 11 years?

I think there's some confusion here. Your Sanyo projector's bulb is a user-replaceable expendable item, meant to be replaced periodically, that slowly dims over it's approximately 1500 hours of use.

You posted in the LCD flat panel forum. LCD flat panel tvs use backlights (or edge lights in the case of some LED backlit models). These are not user replaceable, are not considered expendable, and are vastly more expensive to replace than the projection lamp in your projector.

CCFL backlights are not "bulbs", they are arrays of high-tech flourescent tubes that are commonly expected to go 60,000 hrs before losing half their original brightness, I haven't seen any estimates for LED lighting. In either case the likelihood is that some other part will fail or you will replace the set due to newer technology becoming available long before the backlight fails.

Steve S.
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Old 12-22-2009, 02:33 PM
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Quote:
Originally Posted by MrBobb View Post

Sumbody said a CCFL dims to about 90% of max after 1 year, then stays there until the end of life. UNCONFIRMED.

Not true. After spending years working on equipment that has CCFL backlit touchscreen control panels, I can tell you that normal is they just get dimmer over the life of the bulb until you have to replace the bulb.

Edit: In reference to Steve S above not bulb, tube.
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Old 12-22-2009, 03:27 PM
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This link has a lot of usefull info about LED bulbs.

http://gizmodo.com/5151865/led-bulb-...what-they-seem

Quote:


Based on our experience with incandescent bulbs, when we hear that an LED will last 25-50,000 hours, most of us assume that's when the bulb will burn out. However, that is not the case.

In reality, those claims are really arbitraryno one really knows how to define the lifespan of an LED quite yet. That's because LEDs do not burn out like an incandescent bulb, rather, their brightness slowly fades. So, if the lifespan of your LED is listed at 25,000 hours, that is the point when your bulb will most likely be shining at around 70% capacity (the industry assumes people notice a decrease in brightness at that point). Some engineers have even suggested that lamps should be made that increase power to the LED to combat this problemalthough that would tend to defeat the purpose of an energy saving bulb. It would also decrease the life span of the lamp.

So, the moral of the story is that manufacturers need to come up with a different system to accurately convey the lifespan of their products to incandescent and CFL converts. Personally, I don't think this is much of an issue. I would much rather replace a bulb after 50,000 hours because it got too dim then replace a traditional incandescent after 1000 hours with a bandaged hand because it blew out while I was chopping up something in the kitchen

This is another great link that actually tests the brightness drop off of LED bulbs over time.
(too long to post)

http://www.nickhill.co.uk/white_LED_...xpectancy.html

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Old 12-22-2009, 03:43 PM
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CCFL do lose 10% of their initial brightness and then slowly dim down until they reach 50% of their original brightness, which is considered the end of their usable life. This should take 50K hours.

LED are also rated by their light output over time and should reach 50K hours but LEDs can have their life shorten faster than LED by over driving them and/or letting them get REALLY hot. It is unlikely that the TV manufacturers allow the operation of the LEDs outside of their "safe" zone.

But as we have said before, anything that gives off light, will give off less light over time. LED's claim to fame is lumens/watts, which is better than CCFLs.
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Old 01-01-2010, 07:16 PM - Thread Starter
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Quote:
Originally Posted by Steve S View Post

I think there's some confusion here. Your Sanyo projector's bulb is a user-replaceable expendable item, meant to be replaced periodically, that slowly dims over it's approximately 1500 hours of use.

You posted in the LCD flat panel forum. LCD flat panel tvs use backlights (or edge lights in the case of some LED backlit models). These are not user replaceable, are not considered expendable, and are vastly more expensive to replace than the projection lamp in your projector.

CCFL backlights are not "bulbs", they are arrays of high-tech flourescent tubes that are commonly expected to go 60,000 hrs before losing half their original brightness, I haven't seen any estimates for LED lighting. In either case the likelihood is that some other part will fail or you will replace the set due to newer technology becoming available long before the backlight fails.

Thanks for everyone's comments on this topic. I'm sorry I haven't responded sooner. I didn't know there was as many posts as there was because for some reason I didn't receive an e-mail that a new post had been made.

Anyway, Steve, your post did help me a great deal because I wasn't aware that the LCD's bulb could not be replaced in some way. As you stated, LCD projection must be very different from LCD Flat Panels.

It would be nice to see some generalized curve comparing LCD to LED to understand how each has their brightness dim over time but I haven't been able to find anything. It sounds like they may be close enough to not warrant a comparison.

Ultimately, I still lean strongly toward LED for a reason outside of picture quality, that is, heat. I have seen so many LCDs and Plasma have more than one fan and in some cases let off a huge amount of heat in a room. Obviously they do vary but from what I've seen of LEDs they appear to almost not have any heat. This is pretty attractive to me since I live in the South and I like to keep the rooms of our house fairly cold.

Thanks again for all the help. I do appreciate it.
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Old 01-01-2010, 07:51 PM
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There are no longer any bulb driven LCD rear projection TVs currently for sale that I am aware of.
LCD flat panel TVs that use LED backlighting instead of CCFL backlighting have better contrast espedialy with Blacks and use less power. And the models which have local dimming LED backlighing instead of edgelit LED backlighting are superior in both contrast and power consumption.
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Old 01-01-2010, 09:26 PM
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Quote:
Originally Posted by walford View Post

LCD flat panel TVs that use LED backlighting instead of CCFL backlighting have better contrast espedialy with Blacks

Why would LED backlighting (non-local dimming that is) result in better contrast?
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Old 01-01-2010, 10:01 PM
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Because LEDs can turn off and on completely and almost instantly (strobing) producing very dark blacks and very bright whites. Obviously if the set is not locally-dimmed they have to do this for the entire image, but the overall contrast values are huge.
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Old 01-01-2010, 10:16 PM
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Originally Posted by davegow View Post

Because LEDs can turn off and on completely and almost instantly (strobing) producing very dark blacks and very bright whites. Obviously if the set is not locally-dimmed they have to do this for the entire image, but the overall contrast values are huge.

Let's leave local dimming units out of the discussion. Are you saying that an LCD panel backlit by nonactive LEDs will have higher contrast than a fluorescently backlit panel? Thanks!
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Old 01-01-2010, 11:14 PM
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Quote:
Originally Posted by JP View Post

Because this is likely to make the image worse, not better. Having your light source dim can't be easily rectified by just adjusting something like gamma, contrast, or brightness. I wish you could. Naturally, you would want to calibrate any display out of the box and I suspect calibrating it later might help temper the issue I'm describing a bit but ultimately, it would be best to replace the light source like so many do with a bulb when the dimming becomes pronounced.

For My set I have Gamma, Brightness, Contrast, Ect, I also have a setting for back light that adjusts the brightness of the back light.

It is my understanding that some TV's do have user replaceable CCFL's this site http://www.ccfldirect.com/ sells them, though they only cover the range for laptops and monitors. From what I have read user replaceable CCFL's are pretty uncommon on newer sets, but used to be common enough.

LED and CCFL sets both have a long enough lifetime that it should not be an issue. The average rated lifespan is around 60,000 hours. That just under 14 years of use if it's on 12 hours a day.

The Confusion about LED backlit LCD's and CCFL backlit LCD's seems to be Samsungs fault, thanks to their it's LED TV marketing, it's quite annoying in my opinion.
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Old 01-02-2010, 01:44 AM
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LED's IMO will out perform CCFL's. The bulbs age and yellow over time. They can also develop dark spots. Due to issues I've seen with CCFL's in smaller displays 17"-23" I decided to wait until LED backlit models were out. IF manufacturers made the CCFL bulbs easily serviceable that would possibly be a different story. Plus with local dimming sets the blacks will look so much better in a low lit room.
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Old 01-02-2010, 03:24 AM
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Quote:
Originally Posted by Robin View Post

Let's leave local dimming units out of the discussion. Are you saying that an LCD panel backlit by nonactive LEDs will have higher contrast than a fluorescently backlit panel? Thanks!

There's essentially 3 types of LCD TV's: traditional CCFL backlit, LED edgelit and LED backlit. A few people in this thread seem to be mixing LED edgelit together with LED backlit when they are completely different. AFAIK, there is no such thing as an LED backlit LCD flatpanel TV without local dimming. The point both of them were trying to make, is that LED backlit local dimming LCD's have superior contrast ratios because there are several zones and hundreds of LED's that can be shut off completely... this gives you deeper blacks while maintaining its high light output in bright areas. With CCFL backlit or edgelit LED, the entire backlight would have to be dimmed to achieve deep blacks, but then you sacrifice light output (hence the lower contrast ratio). Some of them have auto-dimming features but many find it annoying and LED backlit with LD is still better.

If there were such a thing as an LED backlit LCD without local dimming, I don't think it would automatically have a better contrast ratio.

edit: I guess there are monitors and notebook screens that are LED without local dimming. As I said above, though, I don't think they would have higher contrast ratios simply because they're LED. The advantages with LED backlit displays -- in terms of PQ -- are because of the local dimming.
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Old 01-02-2010, 03:36 AM
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Quote:
Originally Posted by Robin View Post

Let's leave local dimming units out of the discussion. Are you saying that an LCD panel backlit by nonactive LEDs will have higher contrast than a fluorescently backlit panel? Thanks!

I assume you mean edge-lit? Edge-lit LED's do not inherently provide a higher static contrast ratio compared to CCFL. For example, Apple's IPS based edge-lit LED LCD was tested to have a contrast ratio of 740:1 here, while a similar IPS based CCFL LCD scored a 793:1 contrast ratio here. They look like this:
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Old 01-02-2010, 03:38 AM
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Quote:
Originally Posted by Haelphadreous View Post

It is my understanding that some TV's do have user replaceable CCFL's this site http://www.ccfldirect.com/ sells them, though they only cover the range for laptops and monitors. From what I have read user replaceable CCFL's are pretty uncommon on newer sets, but used to be common enough.

LED and CCFL sets both have a long enough lifetime that it should not be an issue. The average rated lifespan is around 60,000 hours. That just under 14 years of use if it's on 12 hours a day.

The Confusion about LED backlit LCD's and CCFL backlit LCD's seems to be Samsungs fault, thanks to their it's LED TV marketing, it's quite annoying in my opinion.

no, replacing a CCFL in any LCD display is not a simple task, it requires not only dismantling the TV/monitor but also the LCD panel unit it self and you can easily damage the LCD screen or its ribbon cable in the process, the screen is a sheet of 2 panes of glass that are very thin and easy to crack accidentally

I agree samsungs lame LED TV marketing has got so many uninformed people confused and thinking there is a real advantage to their edge lit LED LCD's when in reality the only advantage those TV's got are added life span over a CCFL and in reality from what i've seen on here and in my personal experince with many LCD displays (mostly computer monitors) is that other electronic components inside them fail long before a CCFL goes out by far

i've yet to have an LCD's CCFL bulb burn out and i've got a couple displays hitting the 7 year mark and still work fine, i however have a viewsonic monitor that had 5 capacitors fail in its power supply and it made it look like the CCFL failed but it did not, it was an easy and cheap fix thankfully

all this being said i fully expect that electronics in the TV will fail before the backlight does whether its a CCFL or a LED backlight, most broken LCD TV's i've seen on the net are around 2-3 years old and have either the mainboard, TCON or the panel itself fail in some way causing stuck colored lines on the screen, no image on part of the screen or a messed up looking image on the screen in some way shape or form

If you're a gamer or interested in using an LCD TV as a primary monitor take a look at my thread on Input Lag
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Old 01-02-2010, 06:54 AM
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Quote:
Originally Posted by Robin View Post

Let's leave local dimming units out of the discussion. Are you saying that an LCD panel backlit by nonactive LEDs will have higher contrast than a fluorescently backlit panel? Thanks!

As the responses by others have indicated, there is no simple answer to this question. CCFL LCD TVs can be given good contrast ratios, but the basic advantage of LEDs is that they can be turned on and off so quickly and easily that it is much simpler to achieve good contrast with them than with CCFLs.

We are dealing here with a classic case of new tech (LEDs) still under development competing with a mature old tech. IMO LEDs will soon replace CCFLs just as transistors replaced vacuum tubes in the 50s, and for much the same reasons - simplicity, speed of operation, robustness and reliability over time, size, manufacturing cost, lower energy consumption and associated lower heat. Put another way, solid state usually wins in electronics.
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Old 01-05-2010, 09:45 PM
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I would think LEDS would outlast the panel they are backlighting in many cases. I have items with LEDS that I made before 1970, and they still work. One of them was a power supply I made in 1968 or so, with a big red LED power indicator, that has probably been on for over 30 years of that time period. It looks the same as it always has, it's not really ever been that bright, to be honest about it.

I have had a couple of CCFL monitors that have faded down over the years, but none that couldn't be "fixed" by simply turning the brightness up. Nothing has ever dimmed like one of my CRT monitors did, an NEC that got so dim it took an hour before it was tolerable in a lighted room, and even then, just barely. It was really expensive though, so I lived with it way longer than I should have.
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