Has anyone used a colored (gold/brass) reflector in an LED light?

I was wondering if anyone has ever used a gold or brass colored reflector in a high-powered LED light?

I had a naive (hopefully not ignorant) thought that this may tint the beam a bit, providing a beam color similar to that of a white incan without resorting to lumens-eating window films.

It's a great idea, and there are a few companies doing vacuum gold coatings, but I haven't been able to find a reflector that would work with any light I have.

My guess is that it won't have an effect on the light, since it is REFLECTING the light, not absorbing it at any given frequency. But that's a guess.

Newbie (I think) answered a similar thread several years ago, but I forget the details.

Bill

Thanks for the reply, Bill.

You are right, it may not have an effect. I'll have to search to attempt to find Newbie's post.

I know I've seen shiny brass spray paint, and thought about spraying a spare Maglite reflector (runs a LuxI). If I can find some free time I may give it a try.

It may take some of the greenish tint out of the light. Interesting idea though.

Chronos said:

I was wondering if anyone has ever used a gold or brass colored reflector in a high-powered LED light?

I had a naive (hopefully not ignorant) thought that this may tint the beam a bit, providing a beam color similar to that of a white incan without resorting to lumens-eating window films.

Click to expand...

You are correct that a gold or brass reflector will tint the beam. That happens because those metals will reflect most of the yellow-orange part of the spectrum, while reflecting less (partially absorbing) other parts of the spectrum.

Overall output will be reduced, when compared to a silvered reflector. So, the beam tint should appear less blue-green and more yellow, but also less bright.

The idea is nice, but most of the wavelength emitted from a white LED will
not be reflected.


Link
Link


Tom

From the links posted below, it appears to me that a gold coating would do a very good job of warming the spectrum of a typical white LED without an excessive amount of losses. It also has the advantage of not tarnishing. It does have to be mechanically protected though as it is soft if pure.

taschenlampe said:

The idea is nice, but most of the wavelength emitted from a white LED will
not be reflected.


Link
Link


Tom

Click to expand...

I posted a while back about reflecting a while LED off of a polished piece of copper. It worked pretty well, but it worked by reducing the blue-yellow wavelengths to make the red wavelength more apparent. If you want to actually CONVERT the blue/yellow wavelengths to red, you would need a phosphor. White LEDs (and fluorescent lights) work by converting one wavelength into many by energizing a phosphor coating. The type and amount of phosphor determine what wavelengths are created. Luxeon Warm Whites have a a phosphor that emits more red than most.

This sounds pretty interesting. So if the luxeon warm whites have a phosphor that emits more red than most, what color reflector would be needed to offset that?

I meant that it emits more red than most other LED phosphors. It looks JUST like incandescent light - the whole spectrum is pretty evenly balanced. To make a Warm White look like a regular White LED, you would need to subtract the red, which means using a greenish-blueish reflector.

A colored reflector reflects MORE of its own color and LESS of the others.

So what percentage of light is reflected in an LED-based light? I'm sure there are many variables: emitter type (Luxeon variants vs. Cree vs. Seoul vs. Nichia, etc) and the design of the reflector. However, there may be some generic number that follows the old 80/20 rule.

So for argument's sake, let's say 20% of light emitted strikes the gold colored reflector. The reflector reflects its color, so these photons are tinted with a 'warmer' tint. Is this enough color to then 'warm' the overall beam? Would this then help with color rendition? I would think (amateur here) that most of the reflected light is concentrated in the throw beam, so the long distance beam may be warmer.

You can eliminate the guesswork by reflecting ALL light, Recoil-style. Otherwise, you're probably right... close-up, the beam would be cool surrounded by warm, and at a distance, it would be mostly warm.

-Jason

What is "an excessive amount of losses"?

This is a rough estimation of the loss with a gold covered reflector.
The light above the line of black points will disappear.







Tom

taschenlampe said:

What is "an excessive amount of losses"?

This is a rough estimation of the loss with a gold covered reflector.
The light above the line of black points will disappear.







Tom

Click to expand...

Is that graph raw power output, or is it weighed by the eye's sensitivity? If it's not weighed, the real world effect of that change wouldn't be as much as suggested above, as that blue wavelength isn't as senstive as the yellow/green that would still for the most part get through.

So with a high-powered LED flashlight, it appears I could use a gold or brass colored reflector to obtain the desired tint.

Yes, there would be a loss of overall output. However, can I venture to guess that the overall output would still be greater than if one were to use a tinted film over the window?

It depends on the film. I'm guessing there wouldn't be much of a difference, but I'm not sure.

2xTrinity said:

... Is that graph raw power output, or is it weighed by the eye's sensitivity? ...

Click to expand...

It's straight from the graph of "reflectance of bare gold".
~ 40% at 450nm … ~ 50% at 500nm … ~ 90% at 600nm …


Tom

A typical cool white LED radiates quite a bit of *radiant energy* below 500nm but relatively little light since the eyes sensitivity drops rapidly below 500nm.

taschenlampe said:

It's straight from the graph of "reflectance of bare gold".
~ 40% at 450nm … ~ 50% at 500nm … ~ 90% at 600nm …


Tom

Click to expand...

Chronos;

I have a gold reflector on one of my infrared light systems. It does look impressive.

It is one of the best reflectors for the infrared spectrum.

Larry Cobb

it might be easier to put a filter on the lens than trying to colorise the reflector, and its changable.
i have used a very light yellow filter on the bluish leds, and had it look more like incan , but there is still huge Holes in the total spectrum that were not filled. also used gold mesh, gold filter, and yellow meshes.

green and red dont seem to reflect back on smoke, top skins of water, and fogs, but the RED and the green are very small in the Blue/white leds. so REAL incan, or red or green leds, are better for viewing through some substances, but the White led is BLUE based, your screwed from the get go.
blue seems to bounce off this stuff, and blow right back into your face.

out doors there really is not that much Blue foilage, or dirt, as george carlin would say, there isnt much "blue food".

filtering would be as usefull as the warm leds themselves. warm leds output less "lumens" but if you filtered the non-warm, it would probably be about the same, as the "warm phosphors" in the warm leds they are filtering.

you cannot selectivly filter IN a color,
the color/light had to originally exist. so in effect you would be dampening the blue, which would work great in some situations, i am just indicating that you can't color light that doesn't have those colors in it to begin with .

put a full red only filter over a blue only led, and you get NOTHING.