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

Flashlight Modding and DIY Parts
19

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.

Results:

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 ;-)

20

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.

21

Thanks a lot for this work! I always wondered how much light gets lost in optic and the overlapping bezel.

22

Same here, thanks for the numbers djozz!

23

Well that’s gross….

I was getting away from 20mm triples now just because I want more throw out of the little lights, but man, that’s major. Explains a bit of how hot they get too.

24

Thanks for the test!

I wonder what’s the case with XP-L HI and XP-G3, in my opinion the light loss with the HI is massive, as my triple DD copper sinner 18650 gets host faster where the optic is than where the pill touches the body. Most likely light loss and scattered to the sides but have no way to test it unless I build a “lumen tube”, ceiling bounce won’t be precise for this test.

It seems like searching for good reflectors and hosts will become a top priority from now on, rather than stucking carclo triples and quad into everything. :slight_smile:

25

I made a mistake, just edited the beamshot in post#20

26

Yes. Of coarse we will have light loss through our triple optics. You will have light loss with single emitter reflectors too. There will always be light loss of some sort. Trying to keep photons all rounded up is like herding cats.

Are triples worth it. Let’s compare the same light with single emitter with reflector against a triple optic.

27

I think it’s more what you want the light to do.

  • If want a “pocket rocket” with maximum possible lumens to illuminate a wide area at close range - it’s hard to beat a triple or quad. For the same size light they simply emit more light more efficiently than you can get with a single emitter. They make an excellent choice for an EDC light where you mostly want to illuminate things in a room or your yard. For instance, if you’re trying to vacuum the floor, it is handy to have a light that lights up the entire floor in front of you. A light that most just lights up one spot is less useful.
  • on the other hand if you want a light that can illuminate something a hundred yards away, as well as being useful up close, then a single emitter can be much superior. Overall lumen output may be much less, but you make up for this with a much more intense hotspot.

From Djozz’s testing it sounds like a well-built single-emitter light may have around 15% light loss into the reflector and lens compared to maybe 20% loss into the bezel and optic of a no-lens triple. In my opinion, that 5% difference in efficiency isn’t enough to make a significant contrast between the two types of lights.

28

It will ultimately still come down to mid-lumen throw vs high-lumen flood. But as usual, it’s been a pleasure experimenting for the sake of knowledge. Thanks Djozz!

Yeah, especially when it’s completely overshadowed by three times the emitter lumens.

29

This test is very interesting but let’s not forget about efficiency gain with lower currents with multiple LEDs. According to data from Cree PCT:
Single XP-L HD V6 driven around 10W with Tj=60C (attainable with copper DTP) produces 1165 lm (@10.174W to be precise).
Triple XP-L HD V6 driven at 9.94W produce 1583 lm at the same Tj. Quad XP-L HD V6 driven at 10.01W will output 1681 lm.
That’s around 36% more for triple and 44% for quad. Higher efficiency means less heat and I assume here exactly same junction temps. So even if TIR waste most of this there’s still plenty of gain over single LED with reflector. As to perceived more heat for triples it also can be explained with the LED count - three LEDs have 3 times the contact area so will be more efficient with heat transfer to the radiator so it will heat up faster. This also means LEDs could run slightly cooler compared to single LED so will gain still a few percent of efficiency. If there’s a good cooling all of the above should be quite true and the difference towards multiple LED setup could be even higher. But there’s too many dependent variables to accurately predict in specific case, and with small hosts heat sinking may not be adequate. Someone with required equipment at his disposal would have to test that.

30

I LOVE THIS FORUM.

Just when I think I have an understanding of the variables at work, more information is shared by another member from another part of our planet, that sheds more light (pun intended).

Awesome!

31

Good point. Assuming your light is driven at the same current and is using the same type of emitter, a multi-emitter light should always be more efficient than the single emitter. This is because LEDs are inherently more efficient at low currents.

I think the issue with heat and multi-emitter lights only comes up when they’re heavily driven. You can’t drive a single XPL or Nichia 219C light at 15 amps… the LED simply isn’t capable of pulling that much current. But you can drive a triple or quad at those currents.

32

A nice set of tests, Djozz. Altonx has a point, a more complete picture might be had from finding what drive current it takes to generate the same OTF lumens from various set ups.

Also, polycarbonate is tough stuff but my main concern is that many optics, especially multi-die optics aren’t smooth like a lens but have hollows or other cast shapes that catch debris and are hard to clean. I still use them though.

33

Try the Carclo 10511 optic. Polish the front of it with jeweler’s rouge to remove the frosting. Gives a very pleasant beam pattern closer to that of a traditional reflector light … and unlike the 10507 there are no nooks and crannies for lint to build up in.

34

Thanks djozz!

I believed this to be the case with these triple/quad optics and dedomed/exotic emitters. I used to think even with the ideal LED the efficiency would be exactly similar to an average reflector.

I once built my BLF X6 into the copper 35mm triple (DD XPL) using the Cute-3 optic… Until I turned the light on without the bezel installed. What I saw was an estimated 1/4th of the light spewing out from behind the optic. It soon got modified into a triple reflector setup. I didn’t take any measurements but I’ll say the output went from disappointing to just about right. I used ET D25A reflectors from KD and filed just the lips of the reflectors so they centered perfectly on the MCPCB. There’s no bezel overlap either :+1:

35

Glad you reminded me. I’ve been meaning to do that.
I used to assume that the 10511 was just a 10507 with frosting until comfychair set me straight. Back when Noctigon released the first ever DTP triple board and triple mania began, quite a few people were polishing the Carlco 10511 optics.

36

+1

Thank you djozz for another great thought-provoking contribution. :slight_smile:

37

Interesting read.

38

ever thought of painting the id of the head white?