LED fixture in Theatre?

[gyro_gearloose]

We read too that Leds age quite quickly, with a fairly brisk loss of efficiency.

Maybe that was the case a few years ago, but this situation is improving all the time. For example the LED I used in my Miniscan LED conversion will be at 70% of its original brightness after 100,000 hours of use.

[Nicktaylor]

In a final addition, one aspect not talked about that much is the effect LEDS have on filming with video. I lit a show and as a favour a friend helping, who happened to have his work camera with him filmed it. I have not see the final video, but he said that some of the colours were not being picked up at all!

[the kid]

Have you read Fred Foster's article in February's LSI?

I skimmed this yesterday, it is a great piece, I will look at it some more soon.

 

There are some excellent LED products, but the price is out of all proportion to what they do! My pet worry at the moment is that equipment at somewhere around 5 times the current price is being marketed with replacement light engine capability as a 'benefit'. This, I feel, is a bit of a con. The LED contribution is the reason the cost hike is necessary, so next year or the year after when the newer light engine is available in the new equipment, your two year old one won't match any more, so you have to find budget to upgrade the not yet paid for original? You buy some very expensive stock for your venue - spending perhaps 4 or 5 times the price of the non LED products. Then in an upgrade buy more expensive fixtures that need you to spend more on the old? Can you imagine NOT doing this. You go to the store to find the two you need are old and new, so won't match - how much of a pain will that be?

 

There is every chance they will work it like a printer where the ink is the same price as the actual printer.

[Nicktaylor]

Never buy odd numbers is my motto. Hopefully kit will age a the same speed so trying to match in the future wont come into it. In any case you get the same effect with conventional kit as lamps age and change!

[ramdram]

Ref the relative brightness issue. After a 100,000 hours can a manufacturer really claim, legitimately that is, the loss of efficiency will only be 30%? Has to be a calculated prediction....and stats can be used to prove anything.

 

That's over eleven years use. I would suggest that nobody will keep an Led for eleven years let alone run them. That brings us back to the green issue. Must be huge amounts of parallel R&D going on. How green can that be?

 

The OP might have done his calculations and be satisfied he will get a return but that's only one issue, shirley? I am more interested in how the Leds work and perform and light a production. Yes I might have to change a lamp every now and then but I am confident the "light" will be constant.

 

(Stretching the topic slightly.) I vote we get rid of this green nonsense of no nuclear power stations and simply build them.

 

Cheap, reliable energy; none of this waiting for the wind to blow. Or these galvanic cells atop roofs...be interesting to see how efficient they remain after a few years in the weather of upland areas say...or how roofs were damaged in the rush to get them signed off before whatever date was set. Even more interesting to see how long the guarantee lasts for the entire job.)

[Brian]

... will be at 70% of its original brightness after 100,000 hours of use.

£20 says it won't be.

[hadyn.williams]

... will be at 70% of its original brightness after 100,000 hours of use.

£20 says it won't be.

 

I'll take that bet sir!

 

Plenty of manufacturers are aware that as LED's age you will see a shift in colour and a reduction in Brightness. To counter this, quite a few companies are now using closed feedback loop technology, the idea being that the fixture is constantly monitoring and adjusting it's output so when you dial up say, 5600°K you really do get 5600°K. Not only that but it will be the same across all fixtures as they are all calibrated the same. Similarly, the LED's are never driven at 100% of their output so as they age and dim, the output can be increased to counter the drop in brightness. The first company I saw to do this was Gekko Technology (kit aimed at TV & Film) who patented their system as 'Kleer Colour' I believe. Although I think the Prism kit uses a similar system.

 

I think my views on LED technology are incredibly biased (unfortunately?) since I used to work for a Large lighting distributor selling all the top of the range kit. I was always lucky enough to play with the latest and greatest before it appeared on, or indeed anywhere near the market I always really enjoyed seeing the technology evolve in leaps and bounds. It's so easy to walk round PLASA et al. and see so much flashy trashy LED that's it's so hard to spot what is actually any good or does something little bit clever. Of course, it's also amusing to go to Pro Light and Sound and visit China Town and see all the nice little copies http://www.blue-room.org.uk/public/style_emoticons/default/wink.gif

 

Alot of the stuff I learnt about LED was the energy and economic benefits which extend far beyond lamp life. One example that springs to mind is a comparison between (for example) a 700W discharge washlight, say a Mac 700 and a 700W equivalent LED wash light, let's take VLX as an example. Now when the Mac is at 50%, the lamp if still at full. The VLX is only at 50% at most, and even then that's unlikely. When the Mac is at 0% the lamp may draw back to 400W but with the LED fixture, it really is at 0% except for few electronics.

With colour, if you were to create a saturated colour with a MAC, then the lamp will still be at full but with severely reduced light output due to the colour filter. The LED fixture will be running at a fraction of it's full output, probably while producing a brighter red.

As a rule, LED products have far less to go wrong - a moving LED wash light probably only has had a handful of moving parts - pan & tilt, and maybe a zoom lens. Of course when they do wrong it can be a bit more complicated to fix. Any smart manufacturer stays modular anyway.

Think I wrote an essay on this while I was at Uni...

 

Sadly, I think I also developed LED 'snobbery' for a while. Where I would never even look at an LED par without a scoff, despite the fact, that like everything they are perfectly suited to the right application and budget.

 

Lastly, I leave you wish this: which I think might be the next step with LED. While it uses an LED, the light you see is produced by phosphor - I won't go into the details. Needless to say, when I saw it as a prototype, it was the size of a birdie and looked more tungsten than tungsten http://www.blue-room.org.uk/public/style_emoticons/default/huh.gif

 

Anyway, enough of my rambling.

 

Oh, and no prizes for spotting the various sales pitches in there...

[Modge]

Lastly, I leave you wish this: which I think might be the next step with LED. While it uses an LED, the light you see is produced by phosphor - I won't go into the details. Needless to say, when I saw it as a prototype, it was the size of a birdie and looked more tungsten than tungsten http://www.blue-room.org.uk/public/style_emoticons/default/huh.gif

 

Having just read that (yes, I have better things to do however making fixtures is boring) am I right in thinking at the leap in technology there is not the use of a phosphor per se, but the use of a phosphor separate from the UV light source? I may be in horrible danger of showing my ignorance here, but I was under the impression most (if not all) white LEDs where UV led's with a phosphorescent coating?

 

All that said, if it does what it says on the tin it's very impressive.

[jono9691]

Any company claiming any stat regarding led's @ 100,000 is just guessing! Absolute rubbish. So many variables and conditions to effect the diodes over even a quarter of that time, especially heating up and cooling down a few thousand times. I would be shocked if any of them lasted more than 20,000! and how many times would the fixture need repairing with other problems? 7 shows a week for 8 years, even if the fixture never moved, I would be very suprised.

It' not like any fixture has ever actually been tested for anywhere near that amount of time before release.

[ramdram]

Ref this "new" lamp design tech, mentioned by H.W, very recently I happened to see a lighting unit, to IP56, with remote control, no more than 5" x 4" x 4", say, finished in grey powder coat with cooling fins and yolk...very well made.

 

The actual lighting part appeared (to me anyway) to consist of a plate (say 1/2" x 3/4" square) on which were attached 6 of those LED type elements as you might have in a Lenser torch.

 

Although it was designed to be mains powered it had been tricked up to work with a 12v lead jelly acid battery (motor cycle type). It could produce "all the colours of the rainbow", in flash, slow cycle, you name it it could do it sort of thing. And it was as bright as bright.

 

The guys who owned it, (obtained direct from "their" Chinese source), were dying to play with their new "toy" so did the demo in the pub. The effect was stunning as it went through the built in sequences. The rc was one of those credit card size doodads.

 

No use at all for dramatic type theatre as such but, as an example of the "art" of LED, absolutely perfect for discos, marquees, architectural type stuff (I gather there were bigger sizes). It was almost the (hyperbole alert) acme of perfection...for what it was intended for.

[gyro_gearloose]

Any company claiming any stat regarding led's @ 100,000 is just guessing!

Just guessing? So they don't test batches of LEDs in controlled conditions, for 1,000s of hours? Have a look at this analysis from one LED manufacturer, and scroll down to the 'Reliability' section. Theres plenty of information on how the LEDs are tested, and what the results of those tests are.

 

So many variables and conditions to effect the diodes over even a quarter of that time, especially heating up and cooling down a few thousand times.

Exactly! If you can keep an LED within the manufacturers test conditions, it will last as long as they say it will. The problem comes when LEDs are driven too hard, or are allowed to get too hot. Any LED fixture using high power LEDs must continuously monitor their temperature and take steps to keep them cool, whether that's done by turning on or speeding up any cooling fans, or by electronically dimming the LED, or even turning it off if the temperature cannot be brought down.

 

I would be shocked if any of them lasted more than 20,000!

A working life of 20,000 hours is anywhere from 10-30 times longer than most discharge lamps. LEDs themselves are significantly cheaper than even one discharge lamp, thats why I made my LED Miniscan conversion.

 

and how many times would the fixture need repairing with other problems? 7 shows a week for 8 years, even if the fixture never moved, I would be very suprised.

Having serviced and repaired many different types of moving lights I have to say that most of them problems are down to the use of discharge lamps and the simply vast amounts of heat they generate. Controlling this heat requires fans, and these fans suck in lots of dust and haze fluid which then gets on the lenses reducing light output, will sometimes make nuts and bolts rust, and can, if the fixture is cleaned regularly, block up the fans. The heat also melts wiring looms and cooks stepper motors and drastically shortens their working life.

[jono9691]

Mate!!!!!

 

You know nothing of moving head led and the servicing problems they incur!

 

Go work for a touring company and then bang on!

 

Who cares if the diode can do 100,000 if every other component of the fixture has to be replaced TWICE in that time!

 

I'm not debating that they last longer and have alot less heat, but the spectrum of light output compared to tungsten is frickin rubbish!

Regarding "lasting 20,000 hrs" the vairability of the industry and usage of equipment is so vast its stupid to think anymore than 20% of purchasers will operate it within those limits.

 

As you said, they test for thousands of hours NOT hundreds of thousands of hours! Don't smash on about crap that isn't backed up by facts and real testing for those time frames.

[musht]

>>Just guessing? So they don't test batches of LEDs in controlled conditions, for 1,000s of hours?

 

They do test LED`s for thousands of hours and neccessarily those tests are ongoing, there is only 8760hrs in the average year...

 

Manufacturers don`t like the phrase `guessing` they prefer projected lifespan.

 

Industry standard was 50K hrs to 70% couple of years ago.

 

100khrs is very much a guess.

 

>>So many variables and conditions to effect the diodes over even a quarter of that time, especially heating up and cooling down a few thousand times.

 

LEDs tend to behave differntly outside of their chilled lab thats for sure.

 

>>Exactly! If you can keep an LED within the manufacturers test conditions, it will last as long as they say it will.

 

Manufacturers test conditions can be very hard to replicate in the real world, typical spec trick was to quote output at Temperature Junction,Tj, the very internals of the LED, at 25C, its very difficult to cool the core of an LED this much, lot of thermal resistors on the way to heatsink, way some makers must have acheived it was either running on tiny currents or using exotic liquid coolants.

 

 

>> The problem comes when LEDs are driven too hard, or are allowed to get too hot. Any LED fixture using high power LEDs must continuously monitor their >.temperature and take steps to keep them cool, whether that's done by turning on or speeding up any cooling fans, or by electronically dimming the LED, or even >>turning it off if the temperature cannot be brought down.

 

And the makers output figures are quoted in which circumstance ;-)?

 

>> working life of 20,000 hours is anywhere from 10-30 times longer than most discharge lamps.

 

VLX quotes useable life on its Luminus engines as 10K hours.

 

Short arc discharge can have very short lifespans, but to compare against current LED looking at the larger source discharge lamps in competition where 10-20Khrs for ceramic discharge is not uncommon.

 

>>LEDs themselves are significantly cheaper than even one discharge >>lamp, thats why I made my LED Miniscan >>conversion.

 

Definately depends on the lamp or the LEDs...

Your Miniscan conversion certainly shows that real world experience can be a lot differnt from the expected on paper result :-)

 

and how many times would the fixture need repairing with other problems? 7 shows a week for 8 years, even if the fixture never moved, I would be very suprised.

 

If can seperate the heat from large amount of the mechanics, reliability should increase massively, heat kills the magnets in steppers , crisps the wiring loom and the fans supply a steady source of grime to the internals.

[gyro_gearloose]

Who cares if the diode can do 100,000 if every other component of the fixture has to be replaced TWICE in that time!

Stop buying cheap fixtures then :)

 

As you said, they test for thousands of hours NOT hundreds of thousands of hours! Don't smash on about crap that isn't backed up by facts and real testing for those time frames.

But if the performance output drops at a fixed rate for a hundred, a thousand, and ten thousand hours, then is it really that hard to accept that performance will keep falling at a linear rate? This is not called guesswork, it is called mathematics.

 

And the makers output figures are quoted in which circumstance ;-)?

No, they do almost the exact opposite. The datasheets I've read give details of the LED current de-rating which you must do if the temperature gets too high in order to preserve the life span of the LED.

 

I think this talk of real world vs. lab conditions misses the point a little bit. Like I said in my previous post, if you can keep an LED within whatever operating specs. the manufacturer sets then there is no reason why it won't last as long as they say it will. The problems arise when the LED is allowed to operate beyond these specifications, and this is down to how the fixture manufacturer builds their units and not necessarily down the the LED itself. I will concede that it can be difficult to keep the LED junction temperature down, although the LED I used recommended keeping the junction temperature below 125 degrees in order to achieve the expected 100,000 hour life span :) Its on page four of this datasheet if you want to have a look.

 

Your Miniscan conversion certainly shows that real world experience can be a lot differnt from the expected on paper result :-)

I don't quite follow you, unless you mean that I was surprised when a Miniscan with a 40W, 1500 Lumen LED performed almost as well as one with a 300W, 20,000 Lumen discharge lamp? :D

[musht]

>>But if the performance output drops at a fixed rate for a hundred, a thousand, and ten thousand hours, then is it really that hard to accept that performance will keep falling at a linear rate? This is not called guesswork, it is called mathematics.

 

Its not what happens though, lumen maintainence curve is rarely a straight line, usually fairly sharp drop off in first couple of thousand hours with slowing depreciateion over that.

 

>>>No, they do almost the exact opposite. The datasheets I've read give details of the LED current de-rating which you must do if the temperature gets too high in order to preserve the life span of the LED.

 

Sorry , referring to fixture makers, who will tend to pull out figures under ideal conditions with top bin LEDs.

 

>>I think this talk of real world vs. lab conditions misses the point a little bit.

 

Think projecting life span into decades is theoretical, use of 100k hours is a bit like the hype that accompanied early white LEDs, few of which survive now.

 

>>>Your Miniscan conversion certainly shows that real world experience can be a lot differnt from the expected on paper result :-)

I don't quite follow you, unless you mean that I was surprised when a Miniscan with a 40W, 1500 Lumen LED performed almost as well as one with a 300W, 20,000 Lumen discharge lamp? :D

 

 

Well I was suprised, specially in a Clay Paky which are known for good optics.