The S21D with a side e-switch would be nearly perfect if Convoy ironed out the few kinks in their e-switch UI.
If you already have S21D with 219b 4500k then there is no question I would get the D4v2 with 219b 3500. There is no need to have two 219b 4500k lights imho.
Nichia 219b 3500 has a rich saturated tint that is very nice to look at. It actually is not too yellowish despite of the lower CCT and makes 229b 4500k feel a little too harsh and 519b 4500k a little greenish in back to back comparison.
You would still choose the 219b 3500k over the E21 3500k?
I don’t have E21a 3500k so can’t comment. I do have E21a 4500k, and have compared it to 219b 4500k. But… whether 4500 versions translate to 3500 versions of these 2 LED’s, I do not know.
With white wall hunting E21a 4500 has a yellow greenish ring (see pic above) that 219b 4500 does not have. AFAIK this tint shift ring is why Hank uses frosted optic with E21a and clear optic with 219b. The frosted optic diffuses the ring and makes white-wall beam better looking, but then “hotspot” becomes a little too dim for my taste, and you could still see a hint of yellow tint shift. Having said that, in actual use, to my eyes E21a 4500 is very similar to 219b 4500 with frosted optic, but is greenish at periphery with clear optic.
At any rate for these reasons I do recommend 219b 4500k over E21a 4500 and see no reason to get E21a 4500 unless you see something that I have missed after SO much time wasted comparing :confounded: 
. Get the 219b 3500k, it’s a fantastic alternative to 219b 4500k. Very warm, very pleasant beam color. I love it and wouldn’t want to be without it.
BTW, Carlo Optics for Emisar D4V2 fanboys like me lol/JK. I replaced the frosted optic 10623 in my E21a 4500k with clear 10622 and liked the brighter hotspot much better. I also have 10621 but haven’t had time or a reason to try it yet.
Hank uses frosted optic in E21a 4500k for sure, but I do not know if he uses it for other E21a’s CCT’s. He puts some kind of grey gluee stuff around the legs so be careful not to smear it on the lens. The gluee stuff makes it hard to get the lens out; just use the tip of a needle to pry it out at the edge. And careful with the lens, it falls out and cracks very easily 
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The optics are very inexpensive and fun to play with. I ordered it at the same time I ordered the lights from Hank to save on shipping and avoid the excruciating wait for toys from China.
I replaced the optic in my S21D with the clear Sofirn optic and have found it much more useable so far as well.
I think more useable is subjective to the degree of the TIR lens itself… Any idea what is the degree of the Sofirn TIR?
I don’t think they state it directly but there is good info here including beam shots. That’s where I found out about it.
Yes, I don’t remember seeing Sofirn state it. I mean as in I will use the S21D 60deg TIR inside my house for close range(more flood), while I will use the Sofirn Lens(on beamshot, maybe a 30deg TIR) for my garden(longer range).
Which CCT 519a de-domed is very close to the sw45k?
Thinking about grabbing another S21D now that Simon has them in different CCTs
5700k
But you may have missed your window of opportunity. We cleaned him out yesterday.
5700K dedomed is as close as you'd get. From what I've seen, it has sw45k level rosiness but at a slightly warmer CCT (4100-4300 depending on current).
That’s not glue, it’s the thermal compound used underneath the top aux board. I use a roll of tape and press it down on top of the optics with my thumb to pull optics out of my KR4. A small suction cup would work fine too.
I like 10622 best so far. I would love 10621, but it has a little too much artifacts for me.
Y’all too fast! Sold out :[
Oh so that’s what it is - thanks. Hank had told me when installing the new optic make sure to press it down hard/tight in and that’s why I thought he had put some glue on to hold it down in place.
I searched and did see a post (probably yours?) mentioning the tape method to remove optic, but mine was down really, really tight so I used the hand-sewing needle and just carefully pried the optic up from the edge. I (perhaps a littler over-OCD lol) also didn’t want to leave any tape residue on the surface of optic.
Great review, lots of very useful details. I don’t see the S21D on the AliExpress Convoy store. I’m guessing it should come back eventually. Will there be an option for domed or de-domed, or do you have to explicitly request it?
Thanks. I think it’s just temporary out of stock - maybe getting too popular because it is such a fantastic light for the give-away cost ? I’ve just PM’ed Simon to confirm.
I do not know if Convoy offers custom-order de-domed version of LED in the past (does anyone know?); I’ve asked him about this also.
Right now, I don’t think Simon offers dedomed.
And if you are asking about dedomed 519a 4500k, which when dedomed becomes 3500k (? anyone correct me as needed), a fantastic alternative is 219b in 3500k form. Convoy doesn’t have 219b 3500k but Emisar does Emisar D4V2 High Power LED Flashlight. It is a LED with beautiful beam color and world class CRI of R9080, the very highest rating possible. The magenta tint of 219b 4500k could be too much (too magenta’ish lol) and at times I much prefer the color of 219b 3500k. More calming golden so to speak, without any trace of undesirable green. In other words, as “perfect” a 3500k LED as could be imho.
Based on the too many Nichia comparisons that I’ve done, I suspect whether dedomed 519a 4500k (which I don’t have) is “better” than 219b 3500k will likely come down to personal preference.
Doesn’t dedoming also extend throw and cut back a bit on spill, all things being equal with the same optic?
I enjoy tints that lean rosy, but not too much. A bit more towards golden seems more natural, closer to incandescent. But yeah, the green… I absolutely loathe it. Especially a puke green with yellowish overtones. I’d bought a few lights with tints like that in the deep past, the worst being an Olight M2 Warrior. The artifacts in the beam were also atrocious. Olight has surely come a long way from those days!