Reflector/Side Spill Dynamics?

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gcbryan

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I don't have a bunch of reflectors to play around with or I could probably answer this question myself.

What are the variables with reflector design? I took a small light today and took out the reflector and screwed everything back together and turned the led on. So at that point I'm looking at less light output and it's the overall diameter of the side spill.

So the reflector is what produces the central beam and the light that doesn't get reflected out by the reflector is the side spill.

1) So, what makes the central beam tighter a deeper reflector, a wider reflector, what?

2) How can you reduce side spill. Is this where a lens rather than a reflector would come into play?

I guess these are basic questions but I'm just getting to where I'd like to understand this aspect more completely.
 

Packhorse

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This is a question best suited to a different forum as its a general lighting question instead of a dive light related one. Perhaps you could ask a mod to move it.




Like most ( all ) things I am no expert in optics but hear are my feelings.

When you removed your reflector you did not have less output. What you had was uncontrolled output.

The wider the reflector the more control it has at taming the light beam ( regardless of what desired shape you want).
The deeper the beam ( in relation to the width) the better it will be at producing a more intense hot spot and less spill.
But you can have 2 reflectors of the same width and depth and the shape can be different and as a result produce different beams. So it really comes down to design.

Of course the LED plays a huge part in it.
If you have a LED with a wide dispersion angle then more light can be gathered deeper down in the reflector and help produce a narrower beam.
While a LED with a narrow beam dispersion will push most of the light out the front of the reflector and produce a wider beam of light.
 

Linger

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The more light a reflector catches (being tighter, deeper) the more it can shape into the spot, while anything electrons that go right from emitter and out the front are the spill.

Optics are different in that they shape that light out the front that would otherwise be 'spill' with a reflector. Have a look at some beamshots (see xpg reflector thread in beyond flashlights, LED's, for some reflector and optic pics) and generally optics give a really nice central spot that gradually decreases toward the sides as it tapers off to nothing.
IMHO the best part of optics is that there is no ring around the perimiter of the beam, no strong demarkation of in beam / out of beam, just a gradual increase in illumination.

Optics are ~$1 each, reflectors ~$1.50, you can get a few different styles and have some hands on experience on your test bench.
 

gcbryan

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I did a little experimenting after reading the above replies.

First I remembered the Pelican Recoil led backup that I have with the led reverse mounted on the lens so that all the light goes back into the reflector. I confirmed that what you think will happen does in fact...no side spill.

Next I put a piece of white paper over the lens and turned the light on. It shows a dark area in the center of the lens with all of the bright light in a ring on the perimeter.

I cut a piece of water the size of the dark area and put it on the lens. It does reduce the spill from the center to close to the edges but no matter what you do you can't eliminate the edge spill without eliminating the center beam.

It seems that there would be an easy way to eliminate side spill if you should chose to. I'll have to learn more about aspherics.
 
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