# Luddite or LEDdite?

#### David Ashton

##### Well-Known Member
I have seen many technologies come and go, most promise more than they deliver, and this is why I seem to be continually lowering peoples irrational exuberance when it comes to all things LED.Now I love LEDS, they are great toys and I use them in rock and architectural areas.Now I am told that they are "going to be the future lights of theatre" and "if I saw them I would be convinced"But in areas of science you don't need to see everything as it can be measured.Instead of photometric data like you can get with any reputable theatre light manufacturer one gets emotive language like "pure and vibrant".I actually do scour the websites and look for these breakthroughs but what I see makes me giggle when it describes a wash or whatever.We actually do get the latest Martin and Pulsar gear out here and we have demo's where they shine the light in your face and say "isn't that bright"You never see an iris 4 or a source 4 light in there for comparison.So my plea is, "keep down the hyperbole and work within what is available now so that you don't raise expectations beyond what can be delivered.

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#### soundlight

##### Well-Known Member
Put a 10% transmission factor gel in a source four at the standard 575W, like a good red (12% trans), blue (8% trans), or green (13% trans) cyc silk, and tell me how the difference is then against the LED's with the same color with a spreader lens in them. Even the amber cyc silk is only 32% trans (all of these numbers have been straight out of the rosco swatchbook sitting on my desk).

I have done this test against a few LED products. The LED's are about equal with the S4.

This is where most people don't see how LED's are already working so well.

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#### David Ashton

##### Well-Known Member
OK thats a good start so where can I get the photometric data on these leds?

#### JD

##### Well-Known Member
I realized that Additive & Subtractive mixing might be throwing some of the photometric comparisons off, so I wanted to add a little bit. (There is a great explanation about the two in the link below.)

Subtractive mixing (Usually CMY) is what you have in most movers. Additive mixing (Usually RGB) is what you find in most LED light sources. Here's a quick look using over-simplified numbers. Lets say you have a white light that at a given distance is throwing 10 lux, and an LED par that is throwing 3 lux at the same distance when set it to white. That means the the first light is over three times as bright, right? Not so fast!

The LED RGB fixture may be putting out 1 lux red, 1 lux blue, and 1 lux green. When we gel the white light blue, our transmission factor may be 8%, now our white light is only putting out .8 lux because we have subtracted the other 92% of it's output either with a gel or a CMY subtractive mixer unit. Our LED par is only running one channel (blue) but is now putting out more light than our white light source.

Deep fundamental colors tend to have very low transmission factors and in those areas a lot of light from conventional fixtures needs to be wasted in order to produce the color. An additive mixer like a LED unit wastes almost none of it's output in the same application. So for now, what color you are trying to achieve will dictate what works better. The closer you are to white, the better the older fixtures shine. The closer you are to a deep primary, the better the LEDs shine.

As additive mixing wastes very little light in any color mode, it gets the hands down efficiency award! LEDs can be tuned to create light at the specific primary colors that the human eye detects. (Remember, the eye only sees three colors, the brain fills everything else in.) The ace-in-the-hole for LED units is that you can have a light that can be told to be whatever color you want, is very efficient and has no moving parts!

Color Theory:

#### gafftaper

##### Senior Team
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OK thats a good start so where can I get the photometric data on these leds?
Most of the LED products publish photometric data for white but not anything else. The problem being what color of blue are they testing. It sure would be nice if they would pick a few colors like Rosco Medium Blue and give us a number. Unfortunately they don't. What JD said is very true. Also the colors are far more saturated and intense looking that incandescent.

#### Van

##### CBMod
CB Mods
Most of the LED products publish photometric data for white but not anything else. The problem being what color of blue are they testing. It sure would be nice if they would pick a few colors like Rosco Medium Blue and give us a number. Unfortunately they don't. What JD said is very true. Also the colors are far more saturated and intense looking that incandescent.
Sorry for Necro-threading but I was just doing some catching up. I'm Really, really,really divided about LED fixtures. < for one thing I hate that everyone calls them "Leads" like the metal as opposed to L.E.D.> My biggest issue is one dealing with the color. Now I remember the first time I saw a CMY mixing fixture, a Martin 500 I believe, and the color had a sort of "unnatural" "electric" feel to it but it's a feel that has been accepted into the mainstream now. LED's seem, at least the ones I've seen/tested, to have a similar feel. It's really hard to put into words, it's sort of like the difference between a Leko and a Laser, sure they both have a hard edge, but I wouldn't light with a laser it's wavelength is just goofy. Maybe that's what it is with me and LED fixtures, Maybe a purity of wavelength. Maybe My eyes are just so used to seeing everything through the warm glow of 32K, they just can't handle a new color temp. Anyway that my two cents.

#### JD

##### Well-Known Member
I think Van hit on a point: LEDs are monochromic, much like a laser! Because of that, they do not have a color temperature. It's almost like we are lost, without a home base! For the most part, in lighting, we start with a light source of a specific color temperature (Black Body radiator heated to X k) and we filter it to suit our needs. With LEDs, we synthesize light by mixing the three detectable frequencies into something we perceive as white that has a mathematical equivalent of a color temperature. Depending on exactly what our eyes perceive* as the RGB core frequencies (and that differs from human to human!) , they may look very strange to some people! I am reminded of what I would hear from audiophiles when CDs first came out. "They sound artificial." Many of the tech people would laugh at these audiophiles and tell them they were crazy, but I think they were noticing something. Different people hear differently. The cynic (a guy from Philips /NAP) told me: "That's because without all the background noise and distortion you have no place to set the dynamic range in your mind." He might be right. Who knows. CD's won out because they were more practical, and CD players dropped from over $1000, to$45. Still, his line reminds me of the issue of color temperature. Maybe LEDs seam to be an "unnatural" because they have no natural color temperature! (exempt "white" LEDs, that are a phosphor hybrid and do have a color temp.) As for the long term forecast, I think they will follow the course of CDs for the same exact reasons. (Although there are still people who swear by their vinyl record collections, and will never give them up.)

* Color Perceived: Apparently, the cones on our retina vary in frequency sensitivity in that "true red" or "true blue" is perceived at slightly different frequencies from person to person. There were many articles written about this in relation to photography. For example, to the Asian eye, "white" tends to be a cooler color balance then to the European eye. We had a problem with broadcast video equipment coming over from a Japanese vendor that had a bluish tint. When we contacted a factory rep, he basically indicated that they had been balanced for their domestic market and not the American version of white! I'll always remember that one!

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DarSax and Van

CB Mods