I noticed you have reviews of both, do you prefer S21D with throwy optic or M21B FC40?
Sorry not sure I understand the question. Do you mean my S21D (w/ Nichia LED) that I replaced the stock Convoy 60 Degree TIR with the more throwy Sofirn IF25a TIR?
If so the S21D has less throw but is more floody and is useful around/inside house. Whereas the GT-FC40 Convoy triplets has better throw and more useful as an all-around, âeverythingâ walk light, safety light, etc. Basically 2 different lights so no preference, but personally for example if I have to give someone a gift light, it would be the GT-FC40 lights. Better reach and convenient USB-C charging with M21E and M21F.
Simon said the new 10° optic will have similar throw to FC40, so if both lights are similarly throwy which would you recommend?
Canât say anything definitive until I actually use it but fwiw S21D w/ Nichia and the more throwy Sofirn lens still does not come close (at all) to M21B w/ GT-FC40 LED wrt overall brightness perception and throw.
In addition when you âsqueezeâ all output into the hotspot (for better throw) with a narrow angle TIR lens, the spill/ flood might decrease to a degree that you may not like. IOW there is a price to pay. I think this kind of beam is âunbalancedâ (small bright hotspot, very little spill) but if thatâs what you are looking for then itâs perfect (personal preference).
I like my thrower to have a balanced beam - some hotspot some spill, and thatâs what the GT-FC lights have. It is a unique throwy LED with high CRI and great tint.
Is that with 4x219b, or is 4x519A still not as bright as FC40?
Great point/question (I did sense you were heading this way :) :+1: ). So if I understand you correctly⌠if max output of the 2 lights, S21D with four 219bâs and M21B with one GT-FC40 are similar, both around 2000 lumens (here and here), then how is it I kept saying the S21D does not come remotely close to M21B when it comes to brightness perception and throw? It would be great if S21D with narrow angled TIR equals M21B that way we could just buy the S21D (Nichia 219b with throw!) and forget M21B.
I am absolutely no expert and donât know the definitive answer but do think it has to do with the design difference, 4 LEDâs with TIR (S21D) vs 1 LED with reflector (M21B), the LED itself (one is dome, the other flat), and how lab measurement translates into brightness perception of hotspot and spill. Thatâs the limit of my amateur-level knowledge and any expert here pls chime in as needed if you feel like it.
More importantly though, I can prove my observation: with beam shots of the two lights of an actual scene so you could see for yourself the significant brightness difference. (Pics coming.)
Here we go: M21B w/ single GT-FC40 versus S21D w/ four Nichia 219bâs.
Shot w/ Canon DSLR, identical settings for both lights: ISO 320, f/2.8, 1/3 sec, WB 5000k.
Batteries used were Samsung 40T at full charge for both flashlights.
This is a hill in front of my house and that tree in the middle of the picture is about 30 yards from my camera. Yes unfortunately it does look like that in real life; there is simply no comparison at all wrt brightness and throw. I will post pic of Nichia 519a later but from eyeballing, itâs going to be a âkillâ also. The idea is great, why shouldnât we buy Quad Nichia 219b with throwy optic and skip GT-FC40, but unfortunately the design and LED are not conducive, at least not in a small light.
As much as I love S21D, itâs more useful inside house or close field, and brightness is on low end of flashlights. M21B otoh is useful both inside (because it is quite floody also) and outside (because it has a much, much better throw and brightness). The trio M21B, E, and F have what I call a balanced beam with good hotspot (throw) AND good spill (flood), making them the perfect all-around all-star 
or gift light. Were I to start a collection again, they would be the first light Iâd buy (well together with Nichia 219b 4500k lol).
In my M21B with that XHP70.3 Hi cri is ~95 with Opple and DUV is â0.0020 to â0.0040 depending of output level. CCT averages 5400K. And efficiency is about double to GT-FC40.
Congrats on finding a light you love, but that CCT would be a negative for me. I find beam color above 4500k sterile and âflat.â Even at 5000K my Wurkkos 219c, as neutral as it is, is not a favorite light and barely used. The only time I happily tolerate high CCT is for super throwers like the Wurkkos SBT90.2. Strictly personal preference so no right or wrong.
BTW after my experience with Cree XHP35 HI and XHP70.2 NW (both green hell), I now tend to stay away from Cree LEDâs unless/until trustworthy reviewers discuss the beam color and quality, and even then would only buy it from a vendor that allows easy return like Amazon.
Re. Opple, as much as I love it, as noted above, IMvHO its numbers are no replacement for actual real life observation or photography comparison. So far (ie subject to change with further use) I have found my Opple to read Duvâs that tend to be more negative than what Simon measured.
Double the efficiency of the GT FC40 lmao.
In what universe at similar CCT and CRI?
the 4 LEDs spread their light over a larger area, more dimly. the single LED focuses its light into a smaller area, that is illuminated more brightly
it is a Lumens vs Lux issue:
note both beams are the same total lumens, but spread over different size areas
those beam spread differences also impact battery life. A multi LED light will eat batteries faster, because it is illuminating a wider area, but more dimly, so the operator turns up the Lumens, in hopes of getting more LUX on target. It does not work very well outdoors. More lumens just floods the near field of vision with more light, still failing to project a more intense beam on a more distant target
I also found 5000K LH351D too âwashed outâ. Same for 5000K 219C.
I discovered R9 CRI differences account for it
the 5000K 519a is quite a bit nicer than 5000K 219c and 5000K LH351D, due to higher R9 CRI.
I had that Cree LED, but second version XHP 70.2 ,and in âNeutral Whiteâ CCT. That particular LED was the worst green hell in my light collection. It was going back to Amazon even if the efficiency were quadrupled . Kidding aside, IMHO low efficiency is part and parcel of high CRI with great tint LED (that article you quoted even mentioned it). I am not surprised that any other LED have higher efficiency than GT-FC40 or Nichia; in other words, good to know, but personally, low on the âpriorityâ list.
It seems they have fixed the tint shift for Cree 70.3? For fun, please post pics of beam shots of this 70.3 next to your GT-FC40 and Nichia 219b. I donât care too much for CCT 5400 (too flat and âsterileâ) but would be interesting nevertheless.
BTW with 519a and GT-FC40, preliminary trials with my Opple appear to show Duv MORE negative and Ra ~ 4 points higher than what Simon measured (219b results are closer). Whether this is due to LED variation, measurement difference, or systemic error of the device, I donât know. But personally at this point, other than CCT, I still take other Opple results with a small grain of salt. I trust photography comparison more, for example.
Yeah,Opple is Opple. It isnât lab tool for sure. Iâve bought about 10 different bins of these 70.3 Hiâs for testing. This 2D 90cri is the best one by far. These are domeless, so no tint shift.
Hardest part is to find a bin, that has them all. Tint, cri and effiency. I would have preferred this to be little warmer but this tint is so clean white, that I donât care.
With GT-FC40âs itâs also lottery if you get a good one. I have bought 5 4500K versions at three separate occasions and first 2 of them were good really good, rest were green. I also have 2 3000K versions. Both green. And sustained output and throw of these wasnât enough for my use case.
I will soon receive few more of these. Hopefully they still are the same bin, because they sold out fast last time and I only bought one for testing purposes.
Nice explanation.
I took beam shots of the 2 lights to show the different beam angles. S21D almost 180 degree spread. Still I am a little surprised the difference in throw and overall brightness perception.
The S21D in this picture has the more throwy Sofirn IF25a lens btw.
1. I do find its reading of CCT, brightness, and Ra very helpful (if possibly a little optimistic with the Ra sometimes). Itâs the Duv that I am a little cautious about and I still think back to back âreal lifeâ comparison or photography are more âreliableâ ways to compare LED colors (not Opple Duv reading).
2. Wow - did you buy LED, or are these actually 5 separate Convoy lights :+1: ? If you buy LEDâs, itâs understandable that the bins might be different, as with Cree or any other brand. That said my 4 Convoy GT-FC40 lights have beams that are instantly recognizable as belonging to same family. Even the Duv readings (posted above), if possibly not accurate, are at least consistently negative.
Some are lights, some are separate leds.
I always knew from real-life use that the GT-FC40 has a purple/magenta tint, but have not been able to capture this color on its beam shots (they always look more brownish - see picture above). This has been a puzzle to me, that photography doesnât support what I see.
But Iâve finally cracked the code, by way way UNDER-EXPOSING the central area of the beam, which usually is very bright.
Below are beam shots of my two M21Fâs, one with the very negative (Nichia 219b-range) Duv of â0.015, and the other a more moderate Duv of 0.0050. The magenta/purple tint is clearly captured. Now there is no doubt; finally Iâve exposed the Nichia imitator lol. Equally great that the M21F light with the more negative Duv is actually more magenta ie photography correlates with Oppleâs measurements.
Still burns me how CCT can vary so much with a given emitter, by production batch. Manufacturers really need to aim for greater consistency⌠but, I guess it all comes down to tolerance & demand. There arenât nearly enough people OCD on tint. 