LED Longevity Overrated? - Page 2 - AVS Forum
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Old 09-11-2010, 07:28 AM
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Yeah, I mean my Planar doesn't "seem" to have lost any brightness and it's at 1500 hours, but I'm sure it's quite a lot dimmer than when I started.

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Old 09-11-2010, 08:33 AM
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Quote:
Originally Posted by Alan Gouger View Post

...
I have a proto LED Ive been running now for over two years. So far no light loss or color shift. No reason for me to get rid of this thing I run it day and night without any hick-ups so far...knock on wood. I love the fact I can start it up or shut it down without any ill effect as well as leaving it running when going to dinner.
In the case of the Vango ( unlike the delta )it is liquid cooled and very quiet. Very little heat to hurt the rest of the components. I hope we see others jump on the same bandwagon.

That day "will" come soon when all projection technologies will enjoy the benefits of LED.

Liquid cooling makes a lot of sense. The heat transfer will be better and the temperatures could be lower.
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Old 09-11-2010, 12:23 PM
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No one has mentioned the Samsung LED based RPTV's in this thread. I'm sure some of their owners must have thousands of hours of usage. Do they use a similar light engine and have they shown the alarming dimming talked about here?
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Old 09-11-2010, 01:35 PM
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Next time I talk to tse, I will ask him what kind of longevity testing VDC has done on their pj. Since this is going in gov installs, I assume they have done some kind of testing.

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Old 09-11-2010, 02:38 PM
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Quote:
Originally Posted by millerwill View Post

Is the conventional wisdom still that laser-based illumination is the 'natural' road ahead for lcos pj's, analogous to led being so for dlp? If so, it appears that led/dlp is at least one year ahead of laser/lcos. But maybe worth the wait?

Laser is not specific to LCOS, nor LED to DLP. There are LED LCOS units and laser DLP units.

Laser, being already polarized, is more efficient than LED for use with LCOS, so you'll likely see more of it. But you will also see laser based DLP units, especially in the D-cinema arena, where DLP is currently king:

http://www.dcinematoday.com/dc/PR.aspx?newsID=1783
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Old 09-11-2010, 03:23 PM
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Quote:
Originally Posted by Brandon B View Post

Laser is not specific to LCOS, nor LED to DLP. There are LED LCOS units and laser DLP units.

Laser, being already polarized, is more efficient than LED for use with LCOS, so you'll likely see more of it. But you will also see laser based DLP units, especially in the D-cinema arena, where DLP is currently king:

http://www.dcinematoday.com/dc/PR.aspx?newsID=1783

I am familiar with the polarzied feature you note, but not the reference to the LLE product; thanks much. Is it likely that the LLE laser system will be economic enough to be implemented in home theater pj's, and not only in commercial venues?
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Old 09-11-2010, 05:30 PM
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Well, speaking from experience after extensively using an LED illuminated front projector an average 10 hours per day (approximately 2.500 hours of total usage), i did not notice any difference in brightness from the first day up to the day i sold it, a "lowly" LG HS-201 mini pj equipped with an LED "engine" from Luminus Devices.
I would venture to say that a company like Luminus Devices, which afaik is the main supplier of these LED "engines" for video projection, must have done their homework insofar as having tested their LEDs to the best of their abilities under varying loads, fully on/off and constantly lit for thousands of hours, considering the fact that the company has been working for years optimizing their patented LED technology.
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Old 09-12-2010, 03:45 PM
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I will quote this from a magazine from Cedia last year.
Quote:


The Luminus Devices engineer explained it by saying that "Unlike conventional LEDs, which emit into an epoxy-based encapsulant, PhlatLight LEDS emit directly into air, resulting in significantly longer lifetimes. Phatlights have very low failure rates and median lifetimes that are well above 100k hours under extreme, high-current operating conditions.


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Old 09-12-2010, 04:48 PM
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What do commercial theaters run into on this subject? What is their light source (led, lcd, laser, mercury, etc) and how dim do their pj's get and how soon and do they replace a 'lamp' module?
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Old 09-12-2010, 04:54 PM
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I believe most run several KW (KilloWatt) Xenon lamps.

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Old 09-14-2010, 04:28 PM
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Which typically are good for 1500-2500 hours. Assuming you are talking digital cinema, not film
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Old 09-14-2010, 04:40 PM
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Quote:
Originally Posted by Brandon B View Post

Laser is not specific to LCOS, nor LED to DLP. There are LED LCOS units and laser DLP units.

Laser, being already polarized, is more efficient than LED for use with LCOS, so you'll likely see more of it. But you will also see laser based DLP units, especially in the D-cinema arena, where DLP is currently king:

http://www.dcinematoday.com/dc/PR.aspx?newsID=1783

The article says the speckle issue has been solved it.......that's terrific.

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Old 09-14-2010, 06:05 PM
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Quote:
Originally Posted by Highjinx View Post

The article says the speckle issue has been solved it.......that's terrific.

Agreed! I just hope this system is economical also with home theater pj's, and not only commercial grade ones.
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Old 09-14-2010, 06:35 PM
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I emailed Jim Sullivan from Entertainment Experience regarding the issue. His response is here.

http://www.entexpinc.com/truvue/answers/answers-2.htm

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Old 09-14-2010, 10:01 PM
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Well that was pretty much what I have researched.

Quote:


Because leds are not lamps they do not burn out, so to speak. In fact, they maintain their brightness at close to 100% for up to 20,000 hours

Nice, 100% for close to 20,000 hours for water cooled LED's.

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Old 09-15-2010, 05:42 AM
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This is a relief.

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Old 09-15-2010, 06:30 AM
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I wonder how they produce that kind of marketed lifecycle (20K hours). At normal environmental conditions that would have to tun it for +2 years in an always on condition. How else does one simulate 20K hours in less time?

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Old 09-15-2010, 06:54 AM
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Quote:
Originally Posted by 18628239 View Post

I wonder how they produce that kind of marketed lifecycle (20K hours). At normal environmental conditions that would have to tun it for +2 years in an always on condition. How else does one simulate 20K hours in less time?

The research has been done years ago. LED's are not a new technology.

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Old 09-15-2010, 07:39 AM
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Research for LEDs in general may have been done years ago, but are these LEDs we are talking about general run of the mill LEDs for which the research done years ago were tested upon?

That's like saying you would base research for the flat-head 8 motor as the response to someone asking about longevity for today's 8-cylinder motors.

As such, I would say no one has taken the LEDs in today's LED projectors and run them for a year, constantly, let alone 20K hours.

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Old 09-15-2010, 07:53 AM
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Quote:
Originally Posted by 18628239 View Post

As such, I would say no one has taken the LEDs in today's LED projectors and run them for a year, constantly, let alone 20K hours.

From this very thread:

Quote:
Originally Posted by Alan Gouger View Post

I have a proto LED Ive been running now for over two years. So far no light loss or color shift. No reason for me to get rid of this thing I run it day and night without any hick-ups so far...knock on wood. I love the fact I can start it up or shut it down without any ill effect as well as leaving it running when going to dinner.
In the case of the Vango ( unlike the delta )it is liquid cooled and very quiet. Very little heat to hurt the rest of the components. I hope we see others jump on the same bandwagon.

LED was demonstrated at Cedia 2 years previous to my proto. Not sure when engineering would have started.
I wonder if any of us will ever keep any projector long enough to know if these will go full out to the rated 20K + hours. There are benefits beyond extended lamp life from LED compared to lamp driven devices.
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Old 09-15-2010, 08:12 AM
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FWIW....I know of a Mico that has 1200 hrs run. Its current output, compared to initial install, is still within the margin of error for the readings that were taken at initial install. Basically no output drop of significance in 1200hrs.

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Old 09-15-2010, 08:18 AM
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Quote:
Originally Posted by 18628239 View Post

As such, I would say no one has taken the LEDs in today's LED projectors and run them for a year, constantly, let alone 20K hours.

2 points on that. Firstly, it has been done. Secondly, its not technically necessary as the decay characteristics of Phlatlights, and other LEDs, are not only very well understood, they are very consistent unit to unit.

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Old 09-15-2010, 08:39 AM
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Quote:
Originally Posted by coldmachine View Post

FWIW....I know of a Mico that has 1200 hrs run. Its current output, compared to initial install, is still within the margin of error for the readings that were taken at initial install. Basically no output drop of significance in 1200hrs.

Thx CM !
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Old 09-15-2010, 08:40 AM
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Quote:
Originally Posted by Pastuch View Post

My Benq W5000 hasn't lost any of it's light output after over 1100 hours of bulb usage. It has a sealed light path so I don't have to deal with dust blobs. It has been an exemplary reliable piece of AV equipment. I'm naturally prone to upgraditis and I can honestly say that LED backlights and 3D hold no sway over me. DLP projectors for life!

As another said, you didn't measure. The dimming is so gradual that unless you take regular measurements you won't realize it. I bet when it comes time to replace your lamp, after you put in that new lamp there will be a BIG change in light output.
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Old 09-16-2010, 09:05 AM
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Quote:
Originally Posted by Ericglo View Post

I will quote this from a magazine from Cedia last year.



Just because it turns on after 100,000 hours, doesn't mean it hasn't lost 98% of it's light output.

They make no mention of light output in any of their claims. You are nuts if you think LED's won't dim over time, it will happen.
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Old 09-16-2010, 09:15 AM
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Quote:


They make no mention of light output in any of their claims. You are nuts if you think LED's won't dim over time, it will happen.

My guess is that some other part of the LED projector will wear out or die long before the LED's lose significant brightness.

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Old 09-16-2010, 10:51 AM
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To sum it up, your body`s decay characteristics will vary greatly and are somewhat unpredictable and it is more than likely that some part of your body will wear out before the LEDs in your projector dim noticeably.

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Old 09-16-2010, 11:38 AM
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Here's what the US Department of Energy has to say about LED light source life time;

http://www1.eere.energy.gov/building...measuring.html

U.S. Department of Energy - Energy Efficiency and Renewable Energy
Solid-State Lighting
Measuring Light Source Life

We've all heard the small "pop" as an incandescent lamp fails. It's the sound of the tungsten filament finally breaking as the electric current hits it. This makes it easy to recognize the end of life for an incandescent light source. With fluorescent lamps, end of life may involve flickering or the lamp may simply not activate when the switch is turned on. With LEDs, outright failure of the device is less likely, although it can happen due to component failure. Instead, the LED's light output slowly declines over time.

The lifetimes of traditional light sources are rated through established test procedures. The life testing procedure for compact fluorescent lamps, for example, is published by the Illuminating Engineering Society (IES) as LM-65. It calls for a statistically valid sample of lamps to be tested at an ambient temperature of 25 degrees Celsius using an operating cycle of 3 hours ON and 20 minutes OFF. The point at which half the lamps in the sample have failed is the rated average life for that lamp. For 10,000 hour lamps, this process takes about 15 months.

How are LED lifetimes rated? Life testing for LEDs is impractical due to the long expected lifetimes. Switching is not a determining factor in LED life, so there is no need for the on-off cycling used with other light sources. But even with 24/7 operation, testing an LED for 50,000 hours would take 5.7 years. Because the technology continues to develop and evolve so quickly, products would be obsolete by the time they finished life testing.

A life testing procedure for LEDs is currently under development by the Illuminating Engineering Society of North America (IESNA). The proposed method is based on the idea of "useful life," i.e., the operating time in hours at which the device's light output has declined to a level deemed to no longer meet the needs of the application. For example, for general ambient lighting, the level might be set at 70% of initial lumens. Useful life would be stated as the average number of hours that the LED would operate before depreciating to 70% of initial lumens.

The leading LED manufacturers have begun using the L70 language, stating that their white LEDs "are projected" to have lumen maintenance of greater than 70% on average after 50,000 hours when used in accordance with published guidelines.

Electrical and thermal design of the LED system or fixture determine how long LEDs will last and how much light they will provide. Driving the LED at higher than rated current will increase relative light output but decrease useful life. Operating the LED at higher than design temperature will also decrease useful life significantly.

How do the lifetime projections for LEDs compare to traditional light sources?

Light Source Range of Typical Rated Life (hours)* (varies by specific lamp type) Estimated Useful Life (L70)
Incandescent 750-2,000 -
Halogen incandescent 3,000-4,000 -
Compact fluorescent (CFL) 8,000-10,000 -
Metal halide 7,500-20,000 -
Linear fluorescent 20,000-30,000 -
High-Power White LED - 35,000-50,000

*Source: lamp manufacturer data.
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Old 09-16-2010, 01:14 PM
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Quote:
Originally Posted by mark haflich View Post

To sum it up, your body`s decay characteristics will vary greatly and are somewhat unpredictable and it is more than likely that some part of your body will wear out before the LEDs in your projector dim noticeably.

Good chance of it.
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Old 09-16-2010, 05:52 PM
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One point that a poster mentioned earlier worth reiterating is that "longevity" is but one of several benefits of LED lamp for HT projection.

Even if longevity/life was no different than standard bulb life, LED would STILL be advantageous and still represent a progression of HT image quality. In addition to the wide color gammette, LEDs age along a more linear progression as they lose brightness maintaining better color balance.

Also, and IMO *most importantly*:

* LED brightness can be dialed in negating the need for a mechanical iris to acheive dynamic contrast

* LED has instand on/off ability which allows single-chip DLP to be driven without a mechanical color-wheel completely eliminating spoke time and any hint of "rainbow" artifacts for the majority of viewers who are sensitive to color-wheel discomfort with single-chip DLP designs.

LED may open up the possibility for someone like me, who's bothered by rainbows, to enjoy the crisp image of DLP without compromise. In fact, LED could make single-chip DLP *** BETTER *** than multi-chip DLP. Think about that.

1080p and lossless audio. EVERY BD should have them both.
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