How much would you pay?

The light levels are creeping up all the time now, and the 90W units can replace a discharge source of between 250 and 575W depending on the optical path. The trouble seems to be that they do it by concentrating light output direction, so to produce the Fresnel, the optical design has to be different, or the light quality isn't so good. That ebay one is a joke as I agree, not only doesn't it have a Fresnel lens, it is probably a 60-90W LED source. A friend has been designing a plug in replacement for a type of popular moving light here, that replaces a 150W discharge lamp with an LED cluster and heat sink - I think he's going to market it commercially.

However, my Chinese supplier sent me through today details of all sorts of new products - with some photametric data, and in dollars - the price to me for samples of 750W tungsten equivalents (ETC source 4 beam angle ellipsoidal types) is around $500 each, with fresnel versions soon to be available - so I'd wait a few months, these look very simple designs - just a fresnel lens, or the usual two lens ellipsoidal, and an LED light source. Built in dimmer, DMX controlled.

I'm going to wait a bit and see what happens. There will soon be non-joke versions around.
 
What is doubtful in many photometric or claimed specs as far as light output equivalents is the missing 2 factors of distance and beam angle. Yes, I could say my $40 led flashlight is equivalent in brightness to a 1000 or for that matter a 2000 tungsten. My flashlight has a very narrow beam angle of 6 degrees and measured at 3 feet from the light reading sensor. I can say it is 18,000 lux at 3 feet at THAT distance and is equivalent in point brightness at THAT same distance to a 1000w filament. There are many ways to measure a unit's brightness/lumens/lux/candlepower/ outputs but measuring at a standard reference 3 ft. and ALSO MENTIONING the beam angle goes a long way into representing a true light's brightness. Distance and beam angle should always be mentioned in the specs.
 
Which "ugly" leds have you seen/tried ? Let me guess...the Chinese ones..yes ?
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It's the ones with the LED as the light source.

http://www.oscars.org/science-technology/council/projects/ssl/index.html
A few videos on the right side talk about the present drawbacks of solid state lighting.

That's not to say they will always have poor Color rendition, but right now they are.

Below are direct links to some of the Symposium.
Chromatic Chaos: Part 1 http://c803844.r44.cf2.rackcdn.com/stc_chromatic_1.mp4
Chromatic Chaos: Part 2 http://c803844.r44.cf2.rackcdn.com/stc_chromatic_2.mp4
Chromatic Chaos: Part 3 http://c803844.r44.cf2.rackcdn.com/stc_chromatic_3.mp4
 
Wave of Light said:
That's not to say they will always have poor Color rendition, but right now they are.
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LED and plasma technology are a constantly moving target, so reports/reviews have to be updated frequently to keep with what is happening in the market place. ( or they become historical documents about old tech )

Lots of LED lights are being used on professional shoots.
 
Wave of Light said:
And they look very poor.
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Not everything looks bad. Yes there's lots of junk LED lights being sold, but not everything is junk.

I think like any light source, it takes talent to figure out how to use it properly. I spoke to a CBC ( Canadian national news ) cameraman/producer last Spring, who told me how they had switched over to LED lights for all their location gigs and were completely happy with the results they were getting.
 
 
Movie Mike said:
To this list of essential reading regarding LEDs I would add the following
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Thanks for the link. The LED lights he tests don't appear to be too bad as long as you use them at their rated color balance, and not try to convert them to tungsten balance with a CTO gel that's made for other light sources.

I also found the link to the High Output AC LEDs very interesting, as I hadn't read any reviews fo the ARRI L7 LED Fresnels before. ( LEP light sources sound very promising too )
 
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TheDingo said:
Sorry the forum software borked the URL. I think I've fixed it : High Output AC LEDs ( scroll down to find the ARRI L7 review )
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I read this site a while ago. It has a lot of good information and seems to have been updated since I last looked at it. Some new information which I found of particular interest is that there are immutable laws of physics that mean that there will always be a trade-off between lumen output and color quality in the Phosphor White LEDs used in most LED lighting fixtures. The author uses the recent advances in the Cree XLamp LED emitters to demonstrate that fact. While the XLamp LEDs have gotten brighter, their color rendition has gotten worse. That there seems to be an unavoidable trade-off between brightness color output doesn’t bode well for the use of LEDs in motion picture lighting IMO.

Movie Mike
 
The XL lighting class leds from Cree especially the XM-L and the MTG-2 along with the XPG-2 , do represent a quantum leap in terms of light output per watt (power) ratio. It is the cheap leds often mentioned that give the good (or better) leds a bad name.
Before one can generalize about lumen output vs color quality in leds, one only has to be up to date with the latest advances that are in the making with the led technology especially with Cree. Cree leds do not fall into the "cheapies" category as well as Bridgelux, Luminus, Nichia, Seoul and Phatlight. Articles about leds that are often seen are already outdated by the time the new offerings are commercially available. As an example, the Cree MTG-2 is the updated/improved version of the Hi CRI MTG that that it replaced under a year ago. Here we have a 9mm square single led emitter that operates at 6VDC drawing 3 amps for 18 watts and outputting 1500 lumens for a filament equivalent of approx. 90 watts. Color quality, how about 90 CRI @ 3000K ? Now take 6 of these for a 108 watt draw yet producing over 500W equivalent. Where is the trade-off here ?
 
Norman99 said:
As an example, the Cree MTG-2 is the updated/improved version of the Hi CRI MTG that that it replaced under a year ago. Here we have a 9mm square single led emitter that operates at 6VDC drawing 3 amps for 18 watts and outputting 1500 lumens for a filament equivalent of approx. 90 watts. Color quality, how about 90 CRI @ 3000K ? Now take 6 of these for a 108 watt draw yet producing over 500W equivalent. Where is the trade-off here ?
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I don’t pretend to be an authority on these matters, so I will defer to others. According to this website , the use of CRI to measure the color rendering capability of solid-state lighting for photographic purposes has been widely discredited. It was not designed for photographic purposes, but simply to provide a reference scale for general illumination and has many shortcomings when used to describe luminaries used for photographic applications. A new metric, CQs or Color Quality scale, is under development by the national Institute of standards and technology (nIst) to address the short coming of the CRI index.

For a more accurate indication of the color rendering capability of an LED you must look instead at its’ Spectral Power Distribution graph. If you look at the Spectral Distribution graphs of the Cree XLamps , you will see that the long wavelength colors that are critical to rendering a realistic flesh-tone drop-off appreciably. This deficiency is not reflected the Cree Xlamps’ >90 CRI because these long wavelength colors are not part of the narrow range of standard CRI color patches. Since the rendering of a realistic flesh-tone is paramount in cinematography (whether for film or Digital), CRI is simply not a valid measure of a LED’s color rendering capability for motion picture lighting.

Now, if you compare the Spectral Distribution graphs of the older Cree XLamp MT-G to the newer MT-G2, as they do on this website there is a clear tradeoff of color spectrum for greater lumen output. The 25% greater output of the newer MT-G2 is at the expense of longer wavelength colors. Since, it is the long wavelength colors that make flesh-tones “vibrant,” the additional output of the MT-G2 comes at the expense of flatter, paler flesh-tones. This trade-off is not reflected the MT-G2’s CRI because these long wavelength colors are not part of the narrow range of standard CRI color patches.

Movie Mike
 
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