Design LED fixtures for back & side light?

[HEJL]

Hey Controlbooth,

I have a specific question regarding LED fixtures for back and sidelight. Speaking generally: it's my understanding that I want a two-color mix, typically blue and orange. This typically requires 2 fresnels or pars, positioned near one another.

If I install LED fixtures (likely ETC d40s), can I get both blue and orange out of a single fixture at the same time?

Specifically for back and side light, can I use 1 LED fixture where I would traditionally have used 2 incandescents?

Thank you,
Hejl

 

[JD]

Yes, but with a big qualifier:

LEDs out preform conventionals when looking for or mixing deep colors (especially deep blue), but....
conventionals still out preform LEDs on the colors that are near white.
LED fixtures use additive mixing by nature. Conventional gels are a subtractive mix. Since you are looking for additive mixing, LED fixtures by nature will work better. It is just a question of needing a brute quantity of light. If that is the case, stick with conventionals. I am not sure about your statement about getting two colors at the same time unless you are referring to being able to mix those colors in the same fixture.

For instance, You could develop orange via RGB(AW) mixing and assign it to one submaster, then do the same with cyan and assign it to another submaster, then mix between the two using the submasters.

 

[HEJL]

Thanks JD. I think I understand, so let me clarify and repeat some of that back to you.

Clarifying: We're a small space (40' x 25' blackbox, 17' grid), so I don't think intensity will be a big issue.

And here's what I understand out of what you said (pls forgive, this isn't my area of expertise):

Conventional gels subtract from the white light coming out of the lamp by filtering out every color except the gel color.
LEDs start with individual colors and then add them together to make other colors.

When a designer shines a blue-gelled conventional and an orange-gelled conventional on a part of the stage, that is additive mixing to create a beautiful kind of white.
I assume that this process of subtracting-and-then-adding creates a more beautiful or 3-dimensional kind of light than just two ungelled conventionals would.

If you were to use a Selador Desire LED lamp and create white by additively mixing blue and orange LEDs, would this create the same beautiful white, or would it appear much like an ungelled conventional?
Disregarding light intensity for a moment, would it be significantly better to use a Desire set to blue & and a Desire set to orange? Or can the same beautiful white be created out of a single lamp?

 

[DayOne]

This is a great question. Coming from a physics background, I think I can explain what is happening.

You're looking to get that wonderful purply-white color that comes from mixing something like L119 and R08 lets say. One of the reasons it appears so 3-dimensional is because the light is being produced at two sources. This means that no matter how close you get the sources (a minimum of 12" with a S4 par), there will always be a slight color show around your subject. where blue light can hit the shadow, but amber light cannot, or vice-versa.

With an LED, you can get that wonderful purply-white color. In fact, the way JD recommended to do so is a great idea! Mix your L119 equivalent and program it to one sub and mix your R08 equivalent and program it to another. However, at this point both gel colors are coming from the same source (approximately), and therefore you will not get the same depth to the shadows that you get with conventionals.

Now with something like the Selador Desire LED, you won't mix that same white light with just blue and orange LEDs, you would use the whole range of LEDs that are in the fixture. L119 has many interesting qualities about it, including having a heavy dose of red in the color. This means when you mix L119 in a fixture, it is not just blue LEDs, but also a little red. The same goes for R08. There is a shocking amount of blue in that color as well as green.

To answer your question, you can produce the same beautiful color out of one LED fixture that you can out of two fixtures, it might now have the depth of shadow that you enjoy normally though. I heavily advocate the use of LEDs in theater because of their ease of use, their color palette, and their significant energy savings. Also, their response time is phenomenal.

 

[JD]

Well, using two fixtures to achieve white produces another effect- Since the alignment is never perfect, there are colors hidden in the borders of the shadows cast, even on the actor/actress's face. The result can be a very pleasing way to bring a little extra life to white light. If you are using a single source, such as an LED, the alignment of the light will be too tight to produce that effect, so it will be more like conventional white.

Another factor in the amber/cyan sourcing is that no two gels will ever actually filter a complementary spectrum, so although it appears white, the spectrum of component colors produced in the mix is not the same as an unfiltered light. The result it a non-white white, which may be pleasing to the eye. You may or may not be able to achieve that with an LED source. Hunch is, you could come close, But-

The biggest difference in using LED fixtures is that the primary colors are actually monochromatic. In other words, you are relying on the human eye and brain to synthesize the perception of color. This is why LED fixtures added amber and white to the old RGB formula and are sold as RGBAW units. The white LEDs actually contain a phosphor like a florescent lamp and have a wide bandwidth output. RGB has this problem: Lets say a surface looks orange because it reflects a specific part of the spectrum that falls between red and green. A conventional light will make it look amber. Under RGB LED lighting, the surface may look dark gray! This is because the red wavelength and green wavelength emitted by the LEDs miss the frequency the object is reflecting!

 

[JDurnford2011]

Yes you can get both blue and orange out of a single fixture. This depends though on the LED model your using. In some LEDs you can go to Control Mode and you can select how many channels you want to use. This will typically require an 8 channel fixture though because it divides all of the diodes in half to run seperatley. Works really well with Color bars.

For back and side its ok to use LED light though its usually better to use conventionals as its more natural. On the control mode I mentioned earlier theres usally another setting where you can make it RGBA and this gives it that natural look.

Justin Durnford
Lighting Specialist

 

[danTt]

Can you clarify, because I'm not sure which it is, if you want blue and orange simultaneously out of the same led? or at different times throughout the show.

 

[gafftapegreenia]

Unfortunately, I don't think a single LED fixture will do what you want. What a single LED fixture will do is produce the color of the orange and blue lights AFTER they have mixed. The mid-air affects and shadow effects will be lost. If the light source is one LED instrument, the color mixing either happens internally, or much closer to it than it would if the light source was two separate instruments.