LED vs Discharge

[DjSwirl]

Hi All

 

Sooner or later this subject was going to turn up. I am in a position where I am looking at getting of some new moving heads. I run a small events company mainly for small to medium wedding and private functions. I was looking at standard 250w discharge lamps, MAC 250 are out of my price range, so I have been looking at some of the new LED units that are about, LEDHEAD 90P from MilTec http://www.miltec.org.uk/proddetail.php?prod=MTM-90P which is made by Color Imagination (http://www.color-imagination.com/product/show/?id=82&title=90w-led-moving-head-spot)

 

Where I am having trouble is working out the output, is says “Spot features the revolutionary Luminus CBM-360-W LED lamp (3600 lumens; 6500K; 50,000 hr; CRI=70). The powerful CBM-360-W has an output comparable to a 575W fixture” however they seem to use different calculations then other manufactures (probably for a good reason) so how would I go about trying work out how bright it is in the “real world”

 

Cheers Guys

 

Brian

[peza2010]

I think the be all and end all of comparison is a shootout between what you would like the output to compare with and the units you are looking at buying... numbers are just that, a calculation of output, but it doesnt give you a great idea in a real world situation. see if you can demo the units your looking at and compare with another fixture.

[Brian]

LED lumen output figures are pretty meaningless as are claims about relative brightness.

 

You give the figure of 3,600lm for the unit you are looking at. The manufacturer claims it to be as bright as a 575W unit. A 575W discharge lamp produces 49,000 lumens - ie over 13 times more light.

 

So they only way they can *really* compete is to have optics that are 13 times more efficient. Which is impossible. Or fib. Or use figures under some ideal condition for LEDs.

 

As Peza says, get a demo side by side. Preferably take a long something that you know the real world brightness of as a comparison.

[dbuckley]

The other problem in comparisons is that in the open white position the LEDs often lose quite badly, but as the colours come in the LEDs seem a lot less shabby...

[niclights]

The other problem in comparisons is that in the open white position the LEDs often lose quite badly, but as the colours come in the LEDs seem a lot less shabby...

Except for profiles where the source is white and any other colours are filtered. Here it usually starts bad and just gets worse. Don't forget the beam angle which typically is narrow.

Get a demo and prepare to be disappointed. While there are plenty of contenders for LED wash, the profile still isn't ready (including the Mac350 IMO).

[paulears]

Look at the data

http://www.miltec.org.uk/prodimages/MilTec/ML/mtm-90pl.jpg

http://www.earsmedia.co.uk/krypton.JPG

The unit, is narrower angle, compared to the MAC, yet has significantly lower output.

 

It's good, but not that good.

[timsabre]

LED lumen output figures are pretty meaningless as are claims about relative brightness.

 

You give the figure of 3,600lm for the unit you are looking at. The manufacturer claims it to be as bright as a 575W unit. A 575W discharge lamp produces 49,000 lumens - ie over 13 times more light.

 

So they only way they can *really* compete is to have optics that are 13 times more efficient. Which is impossible. Or fib. Or use figures under some ideal condition for LEDs.

 

I am sure the LED unit will not be as bright, however you've got to take into account that the 575 unit is subtractive colour but the LED is additive. Also the optics of a 575 discharge lamp are usually really inefficient (they can afford to waste a bit, there's plenty of light there), but the LED source is more directionally controlled so the optics will be more efficient. Probably not 13 times more though.

 

For example it's not hard to get an LED fixture on red to beat a red-filtered discharge lamp in terms of light output, as discharge lamps are very weak on red. Same with very deep blues.

[Brian]

Indeed.

 

The real problem is a lack of any sort of standard, or to be accurate the lack of any conforming to existing standards, when quoting light output.

 

There's an interesting discussion about LED manufacturers' claims here on Wikipedia.

[brainwave-generator]

Have recently been touring a mix of Mac700s, Mac 2000s, Mac 3ks, Mac 250 Entours, S4s... then some Mac 101s (LED Mover) and Martin Stagebars.

 

My observation from their use and application, is that on the whole, LEDs are brighter to look into, and at a wider angle. I mean, a Mac2000 will hurt if you look into it too, but it has to be pointed right at you. LEDs when pointed about 30º either side of you still remain very bright, so they are great as crowd-facing fixtures. However, LEDs are pretty useless for actually lighting stuff up. If you want to illuminate a person or an object from 10 metres away, good luck with an LED... a discharge lamp still performs fine.

 

So we used our discharge stuff to light up the stage, and our LEDs to decorate the stage, if that makes sense.

 

For parties and discos, you can do a bit of nice architectural lighting with some LED PAR cans which are very cheap, but for moving colour washes and what not I would still be looking at Mac300s. I know somebody selling some 250s and 300s in good nick for about £500 each if interested.

[peza2010]

then some Mac 101s (LED Mover)

 

I was actually very impressed with the 101's, when the kissy sell out tour came to a venue I was putting PA into...

however as mentioned above, these were rigged on up right scaff bars (ie - pointing directly at the crowd)

good output none the less...

 

and to a certain distance they seemed to have relatively tight beams for a fixture of its type.

[martinw]

Good post here on why you can't rely on lightmeter readings when measuring the output of LEDs either.

 

Martin

[timsabre]

So we used our discharge stuff to light up the stage, and our LEDs to decorate the stage, if that makes sense.

 

I used to think like this, but some of it is useful for lighting things up with now. Some of the LED cyc lighting fixtures are very good.

[niclights]

I am sure the LED unit will not be as bright, however you've got to take into account that the 575 unit is subtractive colour but the LED is additive

 

.....

 

For example it's not hard to get an LED fixture on red to beat a red-filtered discharge lamp in terms of light output, as discharge lamps are very weak on red. Same with very deep blues.

But that's not the case with these profiles. They are subtractive.

 

All the following posts seem to then discuss wash lights for which there are plenty of viable options now. But the OP linked to profiles which are a different matter.

[timsabre]

You're right, I didn't read it properly. Fixtures with white LEDs and colour wheels are really horrible for efficiency.

 

I was thinking of the Luminus CBM-380 which is an RGBW LED (as used x7 in VariLite VLX).

 

It's surprising to me that nobody has yet managed to produce a professional profile fixture using RGBW LED's. Presumably getting the colour mixed evenly is too difficult.

[brainwave-generator]

then some Mac 101s (LED Mover)

 

I was actually very impressed with the 101's, when the kissy sell out tour came to a venue I was putting PA into...

however as mentioned above, these were rigged on up right scaff bars (ie - pointing directly at the crowd)

good output none the less...

 

Did the same for Kings of Leon last week.