Emitter to "Out the front/Torch" Lumens conversion?

[NickDrak]

What is the conversion rate for Emitter vs. Actual "Out the Front" Lumens ratings???

Basically, If a particular manufacturer measures the maximum output for their lights at the emitter @ 100lms, what is actually coming out of the front of the light???

 

[DanielG]

I'm pretty new to this but that sounds like an almost impossible equation.

What type of reflector? OP, SMO? Where is the light in relation to the reflector?

How deep is the reflector? How good is the silvering of the reflector? How "clear" is the lens?

 

[abinok]

Most put the figure at about 65%
multiply bulb lumens by .65 and you have it...
Works pretty good when you realize that the streamlight scorpion (advertized as 100lamp lumens) and the surfire 6P (advertized as 60 OTF lumens) are almost identical in output, and runtime, on the same batteries.

Variables like texture of the reflector (smo vs mop) will change the configuration of the beam, but not the volume of light.

 

[KeyGrip]

The general conversion is .65x. It will vary, but it's a good blanket estimate.

 

[Marduke]

Yeah, generally it's a 2/3 rule. It's closer to 60% for incans which emit light in all directions and there is more reflector loss. Plastic lenses hurt, AR glass helps. LED's help, since they emit more light directly forward. Polished aluminum reflectors are better than painted plastic ones.

In short, 2/3 is a good estimate, but quality lights can push that up a bit better.

 

[NickDrak]

Thanks guys! Just what I was looking for:thumbsup:

 

[WadeF]

I wonder if 65% is too much loss for a LED since it's projecting most of it's light forward. If we can get some confirmed lumen readings from LED lights where the emitter lumens are known, we could come up with a more accurate equation. I know Fenix rates their P3D Rebel100 at 200 emitter lumens, and Chevrofreak has estimated the lumens out the front to be around 145-150, so that would indicate more like 70-75%, or x.70-75.

 

[Marduke]

I wonder if 65% is too much loss for a LED since it's projecting most of it's light forward. If we can get some confirmed lumen readings from LED lights where the emitter lumens are known, we could come up with a more accurate equation. I know Fenix rates their P3D Rebel100 at 200 emitter lumens, and Chevrofreak has estimated the lumens out the front to be around 145-150, so that would indicate more like 70-75%, or x.70-75.

With an good reflector and AR lens, I would believe it. 2/3 is a conservative estimate. Getting more is a pleasant bonus :twothumbs