colored spotlight beams?

[redberet]

Hello everyone.
Seeing some powerful spotlight photos, especially these from PolarLi,

Got me really interested in this subject.
This just might be my new wallet murder hobby, but first I thought I'd ask some question to understand what spotlights are and are not and what they can and can't do to really know if spotlights are really for me.

First, is there a practical way to change the color of the beam from spotlights? I've only seem blueish beams so far.

I'm also into lasers and they can give almost any color.

 

[PolarLi]

Been thinking about color changes myself...
I know it's definitely possible, and I know they use some type of color filters, but that's about it. Here is a video of a 7000 watt Xenon skytracker that show the effect:
If you find the part list or service manual to one of those lights it probably reveal more details.

How do the lasers change color? Different diodes or filters?

 

[FRITZHID]

Different diodes, different crystals in dpss lasers, various gasses in gas lasers and then there are argon ion lasers and the white beam from those can be fractured into several different colors.
As far as coloring a xenon spotlight, quality glass filters are used.

 

[redberet]

Thanks for the info guys. And hi PolarLi. Lasers, at least the modern DPSS and diode based ones I use produce coherent light. Which means all the photons coming out are the same wavelength (say 520, or green), so filters won't work because they block some wavelengths and allow others to pass through, but here you only have one wavelength going through anyhow. Does it mean you need a separate laser source for every color you want? No, you can mix typical green (520nm or 532nm), blue (405-450nm) and red (638-660 nm) laser sources together with dichroic mirror setup to get any color you want. It won't be coherent anymore, but for artistic or visual uses it shouldn't matter, and it will still be a tight source of light with low divergence. And there might be laser sources that produce the color you want itself like yellow or orange (we call them "exotic" lasers), but they are not as mass produced and so are too expensive for most than just combining the standard colored diodes with dichroic mirrors. I can give some more info about building them if you got interested. I usually use lasers for laser projection https://www.youtube.com/watch?v=kZzeUTJDKAU I recently learned about the "laser rainbow" project by Yvette Mattern (last photo in first post) and I actually had a similar idea and thought about building such lasers for the job myself. I estimate the cost at around $5000. But PolarLi, seeing your spotlight shots got me thinking if powerful spotlights with much fatter beams would be a more pleasing for the folks than powerful 10-20W laser beams for since my aim is a only 4km throw distance, which isn't much maybe to use lasers. Now I need to know how much such a project will likely cost with homebuild spotlights instead and if it fits my budget to start learning about them and not spend on laser parts.

 

[PolarLi]

Thanks for laser info!
I haven't seen a outdoor lasershow close up, and if you haven't seen a powerfull spotlight close up, neither of us can really advice each other on how we will perceive and like it. One thing is pictures and videos, another thing is how it looks IRL. There is probably someone around here that has worked with both, that hopefully can shed some light on this. (pun intended) But I will say that a spotlight like the one I made, is primarily not made to be an entertainment thing. (but it is show off for sure ) It still has that practicality aspect I personally find appealing. That was also an important factor when it comes to justify the cost of it. Where's that stunning rainbow laser is a pure entertainment thing, does a better job at that, but can't really be used for anything else. Speaking of price, a very basic short arc spotlight can probably be built for $1000 and up. How much up, depends on how much light you need and other features. If you want to add computer controll, color changes and so on, that will drive the price up alot. With a spotlight you are usually working with bigger and heavier parts that complicates everything that needs to move.
Btw, check your inbox.

 

[FRITZHID]

I've worked with both, lasers for years (+15) and have been dabbling in spotlights for about 5 yrs now.
Both have their place in entertainment as well as just showing off. Lol
There are full built dmx laser systems utilizing dpss and diode lasers combined with x,y servo mixing mirrors, etc. They can get pricy, fast. The largest I ever had the privilege to work on was a 45 watt, RGB dmx with 9 lasers total (3 groups of 3 lasers).
Interesting fact, the red laser is the highest power of the 3 by more then 2x, this is due to red being so much lower in human visible spectrum, green is the weakest power being it appears so much brighter to us.
It is neat to see all three fired up and mixed together for a beautiful white beam shooting on for what seems like forever. Lol

 

[redberet]

To recreate the "laser rainbow" with spotlights, I'll just need 7 spotlights with colored glass filters then I guess.
The laser rainbow is static, so no need to control the angle of the spotlights either I guess.

BTW, they used individual laser sources for each color (well two for the violet, cyan, yellow and orange), not a laser projector. Though I guess you could use that too, which would probably cost >$50000 then.

And just to add to the info, same power blue laser is also perceived less bright than green.
I hear some debate going on about this and people claiming it really depends on the setting, but there are graphs like this:

Two questions now come to my mind:

1) How much power will be lost from each color filter?

2) It's a bit hard comparing brightness of lasers with brightness of spotlight, one is usually expressed in Watts and the other in lumens. So if I went with spotlights I have no idea how many lumens I'd need for a minimum of 4km throw at night with little ambient light.

 

[PolarLi]

1) I have no idea, sorry.

2) It was briefly mention in my thread, it's not so much the lumens that affect the throw, but the size and intensity of the light source. The smaller light source, in this case arc gap, the less divergence you get. But the more lumens you have, the brighter it gets. On top of all this, reflector size play a major part, and focal lenght also comes into play, and the combination of all these things affect how much light you get, and how the beam appears in the air and on a target. For instance, is there a hot spot in the beam? How much spill light do you get, an so on. I just remembered it was some interesting discussions about the subject in ma_sha1 swan blaster thread. Take a look here: http://www.candlepowerforums.com/vb...de-Tank-Light-The-Swan-Blaster-260W-Short-Arc.

 

[DanielCF]

My main expertise is in theatrical lighting. In a theater when you want to color a light you use something called a color gel. I already know what your thinking "but that's just going to block all of the other colors reducing intensity" lucky for you that is not true this is a common misconception the gel does not block the light It absorbs it. I Know your going to ask me "what's the difference" well that involves some basic particle physics. Basicly the absorbed energy excites the electrons in the gel into a higher energy state and when the electrons return to the lower energy state they release light with a wavelength corresponding to the color of gel. note that this does not scatter the beam.

In short yes you can change the color of a spotlight with a relatively low loss of intensity.

 

[FRITZHID]

Idk of to many theaters where the stage is +3km away from the lighting.

 

[PolarLi]

I found some numbers on a website: "Optional colored lenses are available but these will reduce the light output (Red 25% loss, Yellow 10% loss, Blue 12% loss, Green 18% loss). Only available for 2KW through 5KW." http://www.advertisingballoons.com/searchlights.htm
Don't know what type of filters they use.