Light loss in a S2+ triple mod, added similar data for a reflector light in post#8, added data in post#20

I made a mellow S2+ triple shorty with gen.2 92CRI 3000K Oslon Square leds a while ago with a 2x7135 driver (700mA) as a reading light for my girlfriend, and it occurred to me today that with its very flat output it is a good light to measure what the actual light loss is from this common BLF-mod. The typical Carclo 10507 TIR triple optic claims 10% loss, but that is measured with an XP-E size die, and there's the rim at the front that blocks some light too. And I like to use the glass lens to protect the optic from scratching.

I found a piece of flashlight head in my junk pile that had the wrong threading but could conveniently be forced between pill and battery tube so that a bare triple head was constructed for maeasuring the primary amount of light in my integrating sphere. Both set-ups have exact the same regulated current and I suppose the leds put out the same amount of light.

So here are the numbers:

Bare leds: 241 lumen

Assembled S2+ with clear Carclo 10507: 188 lumen. So there's a 22% loss

Assembled S2+ with frosted Carclo 10511: 175 lumen. 7% loss going from clear to frosted

Assembled S2+ with frosted Carclo 10511, stock glass lens added (no AR coating): 164 lumen. 6% loss from the lens

So going from bare leds to an assembled S2+ with clear triple optic and non-ARcoated glass lens will cost you 27% output. (edit: Nichia 219 leds and probably XP-G2 as well do a bit better in this optic, see post#20)

I do not think if measuring the same for a black S2+ host will obtain any different numbers. Using other leds will give slightly different numbers I guess, because the light will enter the optic somewhat different but I doubt the difference will be much.

How much overlap is there around the inside of the bezel (over the edge of the optic)?

I’d imagine, with such small optics, that any little overlap would make a massive difference.

Nice test anyway!

The overlap is there but it would not differ more than a few percent, would it? Mind also that the center part of the little TIR’s is brighter than the reflector part.

Very good data collection djozz. I always wondered how many stray photons were serving a life prison sentence inside thes optic heads.

Wow, almost a quarter of the lumens lost from the optic. That’s significant.

So does this mean that a reflector is more efficient since most of the light is reflected forward?

But the outer edge is responsible for more throw, so that will be slightly compromised. I didn’t think the reflector brightness varied across it’s radius. I may be wrong.

I’d say that’s more than a few percent, but there’s only one way to find out! :smiley:

I will try to think of a way…

Ok, the BLF A6, stock with 5A led, mode 3 of 7, so 100% 7135 controlled and fairly constant:

Bare led: 80.9 lumen

Bare led + white plastic centering ring: 79.7 lumen. So 1.5% loss by the ring

Assembled BLF-A6 with non-AR lens: 67.2 lumen

Assembled BLF-A6 with stock AR-coated lens: 69.1 lumen. So the AR lens gains 2.8%.

So going from the bare led to the assembled stock BLF-A6 with AR-coated lens will cost 14.6% of the light, with non-AR coated lens 17%. Note that the coated lens is 1.5mm, the non-coated lens is 2mm, this will not so much absorb more light but it may cause some extra light loss to the side.

If you calculate back the effect of just the reflector (well, almost, plus loss from the bezel which is as good as completely out of the way in this light), I get 10.3% loss (so 89.7% efficient)

So using this 24mm head tube-style host, in single led form with a reflector it will extract more light (83%) than in triple led form with Carclo triple optic (73%)

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Thanks Djozz for the data.

So what you’re saying is that we need to find about 30% more power for our Fun Build triples to make up for this loss… :))

I’m wondering what the results would be for dedomed or XP-L HI emitters?

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…or set the trees on fire with them for the extra lumens :expressionless:

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Thank you djozz, appreciate the testing and info!

You could always try the triple with a widened bezel (with a file or penknife)…

I would do it myself, but my XPL-HI triple is disassembled for repair.

Either way, 3 XPLs make up for the slight loss in output. })

Great tests! To find out about the overlap contribution, how about taking the bare LED light, putting the optic on top and wrapping it with black electrical tape so no light escapes from the side.

Triple + black electrical tape = fire. Be sure to set it to low. :wink:

Care to tell that story? :slight_smile: Sounds interesting.

I’m with Caleb here. Wow. Thanks for the testing djozz.

Yes, I thought this was a quiet sunday afternoon little pastime project avoiding the things that I really had to do (but were less fun). But since I'm at it anyway here we go, electrical tape, last set of measurements on this subject:

You can see in the top view photo that the electrical tape is not touching the little reflectors (undisturbed yellow reflection)

Here's how it looks in the dark:

The numbers (the flashlight from the OP was disassembled again ) :

Bare leds: 241 lumen. I remeasured it and the output is consistent :-)

Carclo 10507 added, the side packed with electrical tape: 194 lumen.

This is a 19.5% light loss from just the optic so just 80.5% efficiency. I looked up the specsheet for the 10507 and it claims 88.7% for the XP-E and 86% for the Rebel. It sounds logical optically that the bigger the die, the less efficient the optic because a bigger part of the object is not in the best imaged middle.

This also implies that the flashlight head, blocking part of the optic, just eats up 3.1% of the light, so that is not as dramatic as it may look like.

I had another thought: the flashlight from the OP has gen.2 Oslon Square leds which have a funny-shaped dome that perhaps messes with the optic?:

I have another (coincidentally also red coloured) S2+ triple mod with 3000K Nichia 219C leds. I wondered if the 10507 has a different efficiency for those. So I did the same electrical tape measurement with the 219C light as was done with the Oslon Square light. I chose also a steady low mode for this.


Bare leds: 82.5 lumen

Carclo 10507 added, the side packed with electrical tape: 69.4 lumen

So that is 84.1% efficiency, quite a lot better than the 80.5% from the Oslons! And actually the beams from the two lights would have given a clue already, the 219C beam has a narrower tidier hotspot than the Oslon Square beam (left Osram Oslon Square beam, right Nichia 219C beam, the Oslon beam was a bit brighter, but you can still see the difference, and better in reality) :

Could it be that the XP-L Hi with its messy beam through the 10507 has an efficiency even under 80%? Well, I'm not going to find out, I've done enough of these measurements now ;-)

Edit: aaarrggh, messed up the last beamshot, forgot that the Oslon Square light had its frosted optic back. Had to change that for a clear 10507 and here is the real comparison:

So the Oslon actually gives a tighter hotspot than the Nichia 219, but still more light is lost through the optic. It is getting too complicated for me now ;-)

Great testing DJozz.

That said, there are a number of things that can be done to reduce the light loss:

  • Do not use a lens - The optical acrylic in Carclo optics is strong stuff. Many lights use optical acrylic as their lens material and don’t have glass on top. Adding a lens on top of a Carclo optic is unnecessary. I have a number of small triples where the optic is exposed at the front of the light and the light is loose in my pocket with my keys. I’ve yet to suffer any damage to the optic. And if by some chance the optic did get damaged. it’s actually cheaper to buy a new 10507 optic than it is to buy a new AR coated glass lens.
  • Use a host that doesn’t hide so much of the lens - The Convoy S2+ hides a bit more of the optic than some other lights. While some part of the edge hidden is unavoidable, it is possible to reduce the light loss seen in the Convoy. Alternatively, you could file down the inside bezel of the Convoy to reveal more of the optic. This might make your light look like crap though.
  • Different emitter - I’m not sure this would make a difference, but it might. Carclo rates their optics at 10% loss with XPE, while Djozz tested 20% with Oslon Square, and 16% with Nichia 219C. I wonder how other emitters fare under these optics. XPL HI? XPG2 and 3?, Nichia 219B? Presumably smaller dies would see less light loss.

The combination of not using an outer lens and using a more revealing bezel should reduce the light loss from almost 30% to around 20…. much closer to the 14 loss seen in a typical reflector light with AR coated lens.