Making tri LED fixtures 'deeper' in colour

[Jamtastic3]

HI BR.

 

OK bit random this one...

Got some Tri LED pars - OK fixtures except the blue and the red are brighter in temperature than I realised. I'm just wondering if there's a gel I could use to put over the whole front of the par that will make the blue and red slightly deeper in colour temperature but not effect the overall output too much and not make the green too murky. I'm looking for that nice deep blue LED output and also a rich red output that's deeper than primary red.

 

I could be asking for too much here but I throw it out to you guys.

 

Cheers!

[adam2]

I dont believe that what you want can be done.

A suitable filter could be used to make the blue deeper or more saturated, by blocking any green that was "contaminating" the blue. This would not only noticely reduce the blue output but would almost eliminate the green and red.

Likewise a suitable filter could probably render the red more saturated, but would block almost all the green and blue.

[gareth]

What Adam said. As soon as you start using filters to block out bits of the spectrum to 'tune up' one colour, you're going to start buggering up the other colours.

[Brian]

^^^^^What they said.

 

Think of it like this. You have a light source with a certain spectrum...

 

 

It's 'brightness', or total power output, is the amount of energy (= area) under the curve.

 

You want to alter the spectrum to fit another curve...

 

 

The only tool we have to do this (realistically) are filters which work by attenuating different frequencies of light as they pass through it.

 

So, to match the top spectrum to the bottom one we must attenuate each frequency by a specific amount until they match. The amount we attenuate each one then defines the curve we need for our filter's spectrum.

 

Or, put another way, the spectrum of the filter is the difference between the two curves.

 

However, if you think about this a few things should stand out...

 

1) We can only attenuate a given frequency. So whilst we end up matching the same shape, the absolute intensity of a given colour will often have to be reduced.

 

2) Because of 1) the area under the new curve will always be smaller than the original. This means the total power is going to be less (=less bright).

 

 

If you look at the two spectra above, both have peaks at around 450nm. However, the only way to make the second from the first is to attenuate that peak down to match the other one so reducing intensity. What we can't do is boost the other frequency up in intensity.

[Don Allen]

Did not get to keep any samples at Entech but the LEE led gels are designed to do that from what I remember. The 117 steel blue was a weird yellow colour because it was designed as a colour corrector to take an led 117 to a tungsten 117. LEE led filters see what I mean ?

[Shez]

I think those Lee LED filters are designed to be used with white LED fixtures, not coloured ones.

[adam2]

I think those Lee LED filters are designed to be used with white LED fixtures, not coloured ones.

 

Yes.

[gareth]

I think those Lee LED filters are designed to be used with white LED fixtures, not coloured ones.

 

Indeed they are. The idea is that you use them with a cool white (>6000k) LED source, and the effect is similar to putting the 'regular' filter of the same number in front of a 3200k tungsten source. The trouble is, there's so much of the spectrum missing from a cool white LED in the first place that much of the time you're trying to recreate colours that consist largely of the bits of the spectrum that are missing, or present at much lower levels.

[timsabre]

I think those Lee LED filters are designed to be used with white LED fixtures, not coloured ones.

 

Indeed they are. The idea is that you use them with a cool white (>6000k) LED source, and the effect is similar to putting the 'regular' filter of the same number in front of a 3200k tungsten source. The trouble is, there's so much of the spectrum missing from a cool white LED in the first place that much of the time you're trying to recreate colours that consist largely of the bits of the spectrum that are missing, or present at much lower levels.

 

Yes... when shone on a white surface as in the Lee demo video, they seem to work very well. On differently coloured objects the results can be wildly different from the tungsten equivalent.

[vinntec]

And just following on from spectrum discussion you need to remember that you are also starting out with a much narrower spectrum in the first place which is covered by your RGB emitters (compared to a tungsten lamp for example). So there are places you can't go at all whatever you do by attenuating with filters.

 

We have used a mixture of different RGB and RGBW lanterns in the last year or so at our tiny theatre and they have proved immensly useful for giving a punch of deep colour, especially where the precise shade does not matter. We certainly don't try to light faces with them but have found we can balance different makes pretty well to each other. We do almost exclusively plays here, so they have worked despite being in an unpromising subject area!

 

We are now looking into extending this experience with some of the Selecon PL1 range (with which I have no self interest) which are deliberately designed to cover a much wider spectrum so will mimic a lot more favourite gel colours than a typical RGB lantern (and obviously cost a lot more).

 

Peter

[indyld]

As we do not have the equivalent gain 'boost' ability of the sound department when it comes to light frequencies/wavelengths (See Bryan above), an option would be to try using gravitational red shift to alter the output.

 

Unfortunately, in my experience a theatre of the size to use those LED PARs is unlikely to have room from an enormous planet, blackhole or similar entity to do the job. There generally isn't enough wing space.

 

E2A: Am now wasting time wondering how to utilise the Doppler effect to achieve this when I should be prepping for a lecture.

[Brian]

...utilise the Doppler effect...

Mount the units on a track guided trolley so they can move towards or away form the stage at high speed? Of course, you need double the number of units so you can alternate them whilst they are moving back to the start position.

[MarfaLights]

...utilise the Doppler effect...

Mount the units on a track guided trolley so they can move towards or away form the stage at high speed?

 

On the plus side, your kit gets smaller as it approaches the speed of light.

 

 

 

[alistermorton]

Although sadly the loading on the truss increases, too, as the mass goes through the ceiling.

[Dmills]

And cue timing gets **really** tricky, as all those varying accelrations play havoc with the reference frames.

 

Further, remember how dancers are well known for being able to trip over their own shadows? Well now add significant (and time varying) gravitational shear! I am afraid that on that basis it is not going to pass risk assessment here.

 

Regards, Dan.