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NAB 2013: Properly engineered LEDs


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#1 Phil Rhodes

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Posted 09 April 2013 - 08:17 PM

I've spent a while today walking around all of the places hawking LED lights - which is a lot of places - challenging each of them to explain why their particular LED lighting devices produce acceptable colour rendering for film and TV work, given that we now know the traditional CRI assessment does not adequately characterise discontinuous-spectrum sources in that regard.

 

Most places responded with phrases along the lines of "It's got high CRI, stop asking awkward questions. The one single outfit that didn't was the Danish company Brother, Brother and Sons, who make the Area 48 softlight. Four of them look like this:

 

bbs_light.jpg

 

Since the scale isn't necessarily Each subunit is about a foot on the long side. The diffuser is actually a phosphorized panel that's removable. Taken off, you can see the blue LED emitter elements which drive the phosphor:

 

bbs_open.jpg

 

They're so intense, there's a safety interlock to prevent you burning a regular pattern of little holes in your retina when the phosphor panel is removed.

 

This is good, because you can remove the phosphor panel and replace it with one which produces a different colour temperature, or even, soon, coloured light for effects or illuminating chromakey screens. This approach also gives the company a lot more granular control over how the things behave, since it can specify any phosphor for the panel and develop those phosphors independently of the LED driver technology. Most approaches rely on an LED driver that's a solid block of plastic with the phosphor and diode junction sealed inside, which is much less flexible. The company also makes all the right noises about thermal management (and remember the phosphor isn't attached to the heat-generating LED in any case), including making it clear that you can leave them on for hours in an un-air-conditioned barn in Death Valley in August and they won't get dimmer as the thermal management circuitry kicks in.

 

Now, this isn't the first time this has been shown (they were at BVE in London a few weeks ago), but it is the first time I've ever had anyone correctly refer to the much more recent Television Lighting Consistency Index (read about it in this EBU article). While this is really designed quite specifically to evaluate lighting for television, TLCI certainly a much more comprehensive analysis than CRI and any light which scores high for TLCI is much more likely to be suitable for critical work.

 

You could complain that the Area 48 light is a bit of a large, heavy lump, but it's certainly sturdy and a large amount of the bulk about heat dissipation.

 

So, cheerful-looking Peter Plesner, CEO, full marks!

 

bbs_plesner.jpg

 

P


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#2 Adrian Sierkowski

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Posted 10 April 2013 - 06:24 AM

Phil, how rugged was this phosphor slide thing? Did it seem flimsy in a "i'm terrified to put this in the back of my truck at 3 am in the dark desert because it'll break" type way?


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#3 Phil Rhodes

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Posted 10 April 2013 - 12:37 PM

It looks like a chunk of eighth-inch plexiglass with the typical yellow phosphor colour, when it's not illuminated - I didn't ask what it's made out of, but I can probably drop by and find out. If it's polycarbonate it'll be very tough. I suspect you'd want to put it in some sort of slip case, at least, to avoid it getting scratched.


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#4 Kieran Scannell

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Posted 10 April 2013 - 02:46 PM

Good find Phil! Did you talk prices? Not that I'll be investing in 2013:-)


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Rig Wheels Passport

Metropolis Post

Visual Products