A couple months ago we had the above exchange - the question was about behavior of 8A Buck versus 12A FET, the 2 versions of Convoy S21D. Thanks to @bilakos10’s review of the FET 12A HERE, we now have an approximate answer, and it looks like stephenk hit it on the nose. :+1:
The 12A FET driver indeed has a brighter max start ~2800 lm, but then stepdowns quickly and rather drastically, to 350 lm, 12% of max after just 2 minutes.
The yellow letter X superimposed on bilakos10’s 12A FET graph represent numbers from the 8A Buck version of the light. They are approximate ceiling bounce numbers, where I assumed 100% is 2000 lumens. Even though the 8A Buck is not as bright at start, it has a much more gradual and gentle stepdown. In addition, it sustains brightness much better, settling in at ~750 lm.
Looking at the above runtime graph reminds me of this puzzle, a question I always have about my Convoy: if the thermal limit is set at 55°, why do I measure 60° at the head during my runtime tests?. In fact during my runtime comparisons, the Convoy always measures the hottest among the lights I have. Most lights stays at 40-50° at the head, versus 60°.
Here is my attempt at explaining this discrepancy. Essentially it is true what Simon says, there is a thermal limit of 55° and it does trigger stepdown. However the stepdown is limited to a power level that is preset at factory. This level is fixed, regardless of what the temperature is. This would explain why my Anduril lights are all over the place with brightness output, and my Convoy is a flatline with hardly any up or down regulation.
Not complaining at all. The flat output is one reason why I love my Convoy’s. Anyway, I am not sure if my “theory” is correct at all. Please take the “explanation” with a table-size grain of salt and correct me as needed.
Flashlight porn to spice up this somewhat dry topic. I have dual citizenship lol so you’ll have to put up with my love for Emisar D4V2. They are like little jewels that fit perfect, PERFECT, in the hands. Enjoy your Convoy but do get an Emisar one of these days to know what the hype is about .
My question would be which light will be able to sustain a higher output on identical leds, the S12D with the 8A buck driver or a D4K/D4 with the 8A boost driver.
Interesting discussion. I made some comparison of S21D versus D4V2 previously, but only with the NON-boost driver version of my D4V2.
I am not sure if the sustained brightness is related to the driver, or more to the stepdown algorithm that Convoy uses (basically a fixed lower limit that a Convoy light will not go lower, regardles of temp)? In other words, if D4V2 with boost driver has the same thermal regulation algorithm as the non-Boost, wouldn’t it step down just as much?
Looking at S21D FET vs S21D Buck above, I wonder the same thing. Is the drastic runtime difference due to difference in driver, or difference in thermal regulation algorithm? I didn’t think flashlight could be so complicated and interesting.
Right, back to the green vs purple AR glass. This is my testing with Convoy S21Es on 40% mode, hotspot measurement. Opple Lightmaster 3 Pro.
2700k green AR 2681k 97.9Ra +0.0010 DUV
5700k green AR 5147k 98.1Ra –0.0013 DUV
5700k purple AR 5157k 98.3Ra +0.0018 DUV
The lens switch is between 2 & 3 right? If so, that’s about a 30 point raise in the Duv? We are getting results that are very close. Mine has been about a 20 point raise from green to purple (not purple to green lol - I’m confused, and can be confusing).
Sorry for the confusion. My D4V2’s are all regular, NON-boost version. AFAIK this means CC 9A for the 219b D4V2, and CC 5A for the E21a D4V2.
Yes, the lens switch (both Convoy lenses) is 2 to 3. I took a few measurements and would say there is a +/- 0.0006 margin of error of hotspot aiming. There is certainly a significant difference between the Purple and Green, though both are perfectly neutral when not compared side by side. The purple had marginally higher lux, but the difference was not significant.
Thank you. I did another round of testing with new AR purple and Non-AR lenses that fit S21D (I bought just for testing). Results again follow the same trend: 1. From our findings, AR Green drops Duv about 20-30 points from AR Purple. 2. It may also decrease Duv from non-AR lens and from no-lens, but to a much lesser degree. I call this “active-rosying” lol. 3. AR Green is not as good at light transmission vs Purple, but we are talking about 3-4 percent - not relevant from Nichia hobbyists’ perspective, and for example absolutely nothing compared to stepdown loss. I do use AR Purple when I am trying to hit 1000m throw for my TS30S for example, but that’s about the only time I care.
I have not had so much fun with flashlight since I got the Opple. And I am glad you got one too to confirm and thanks for doing the test.
Are we the first people who quantify Duv change of AR Green vs AR purple? :+1: That would be cool.
During the lens comparison I noticed Duv would drift downward the longer the LED is on. As if it’s part of warming up. Because I have nothing better to do I ran another test to see how much and how fast this drift is.
These are numbers from S21D with Nichia 219b 4500k. Brightness is 2 down from max, 10% (?). The light is on tripod as usual and in this setup I could see x,y coordinates drifting slowly 1 or 2 points at a time (4th significant figure).
So Duv dropped about 12 points while the LED is heating up, and was still drifting slowly when I got bore and terminated test. I’ve seen the same thing with my 519a LED. (EDIT @ 25 min)
The drop in duv and rise in CCT seems to suggest that more blue is leaking through the phosphor--I guess the phosphor has slightly worse performance when hot.
Another related (?) phenomenon I observed yesterday: I was messing with a Convoy S2+ 519A triple running on a 4-mode 5A driver and protected 5A battery. I've had the light for a month and used the turbo lightly, no issues. Yesterday I ran it a bit too hot, and it tripped the cell's protection circuit! I guess that heat somehow also causes higher current draw (through lowering forward voltage), which might also cause more blue to leak out as the phosphor comes closer to being saturated.
From AR lens Duv comparison to Duv drop with time and heat, the last couple pages of this thread contain the most fun and relevant discussion for me, all thanks to the humble Opple. And the tests are easy: the main thing is to NOT move the light or sensor once you’ve set them on stable platform. I repeated test, but with Nichia 519a 4500k, 10 degree clear lens, brightness 20%. Sensor 12 inches from light.
The Duv drops ~20 points after 30 minutes, even more than with 219b. Now I know, if I do the “wave test” (waving the light on the Opple) I will get a more positive Duv.
As LED heats up, CCT of 519a goes down, in opposite direction to 219b.
I previously wrote that the beam of 519a 4500k has a golden tone here, now I know why it does. The actual CCT of my 519a 4500k is ~3800k (plan to re-test with 60 Degree Bead lens). This LED should really be compared to 219b 3500k, not 4500k.
Flashlight fun pic , my beloved Emisar D4V2’s (background is a To’ere slit drum btw). These guys I keep in my bedroom because they are pretty, especially with the aux lights on full blast, parasitic drain be damned lol. The knurling and matte anodized finish are truly first class.
The pink aux light is actually my most favorite (in the sand colored Emisar). Somehow it sparkles more to my eyes, diamond like.
PS I know these are not Convoy but lots of us do have dual Convoy-Emisar “citizenship.”
Can’t agree more. I love my Emisars and Noctigons, but that doesn’t mean I don’t love the S2+ Convoy triples I’ve built. To quote something I’ve read here on BLF, “S2+’s multiply like rabbits” (or something to that effect).
A purple AR lens is advantageous when the LED is already rosy or too rosy.
I swapped out many purple AR lenses to green, but left it in my triple 219B sw45k flashlight since it was already very rosy. Same with dedomed 519A LEDs since they are very rosy.
(Relevant/interesting post from my other Convoy thread)
From Turbo start, percentage of max brightness where each flashlight settles after stepdowns (in general within 10 minutes after start) using ceiling bounce method. I checked these numbers because for the way I use my flashlight (as a walk light, duration ~50 min), where the light settles (the sustained brightness) is most important. Lights that settle at too low level are not good for me because then I would have to re-push button, then it would get dim again etc.
As some of us have observed, Convoy lights tend to settle at highest level, that’s partly why I love them. All Convoy lights stay bright but the Convoy H2 headlamp with Nichia 219b in particular is fantastic and extremely highly recommended as headlamp for evening walk/exploration (keep in mind it is heavy so you need to buy headstrap with a top strap like this one). The Nitecore MH12S, one of my favorite throw lights, is not bad.
The few Anduril lights that I have tend to settle at the lowest percentage, especially Wurkkos, even after thermal limit has been raised. But note that 16% of the monster SBT90.2 LED in the Wurkkos is still the brightest light in my collection .
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, my beloved Emisar D4V2’s (background is a To’ere slit drum btw). These guys I keep in my bedroom because they are pretty, especially with the aux lights on full blast, parasitic drain be damned lol. The knurling and matte anodized finish are truly first class.
