Convoy S21D w/ legendary Nichia 219b :) - Review & comparison w/ Nichia 519a, E21a & other lights with Nichia LEDs incl. Emisar D4V2, Convoy S21F. (Summary & measurements on P. 1)

Thank you so much for the data! I must say that I am very surprised by how little the green AR on Convoy lens changes the tint.

Regarding your question: I think green AR helps with tint shift precisely because it does not affect the periphery much. In a typical TIR setup, the beam tends to be greener at the center and pinkish at the boundary. A good green AR lens should take out much green from the center but not remove green from the boundary, thereby eliminating tint shift.

The 519As actually start out without too much shift (way less than the 219Cs that were in my light before), and however much shift that does occur cannot be accurately captured by a camera, so I couldn't make a reliable comparison to your beamshots, unfortunately. My 5700K triple is under medium spot frosted (Carclo 10508) TIRs, and with a non-coated glass the tint shift is ok enough that you probably won't notice unless you know it's there. With a purple AR, however, the beam turns to fried egg and the tint shift is very obvious on a white wall and in real world use.

It’s numerically small but is noticeable as other users have noted (stephenk above). I am glad that my result is in the range of Djozz’s test. His change between green and purple was about .003, mine is .002.

For those new to this you could very roughly see what the change in beam color is by enlarging the pic below and look at the color field that each of the dot is in. It does become a little more yellow-green with the purple AR lens.

I plan to take A vs B picture of actual scene (wall of truth in my living room :slight_smile: ) for further comparison between green and purple.

another data point:

.

The data jon_slider linked is very interesting, in contrast to cannga's data, as the purple AR appears to have less of an effect compared to green AR. Perhaps variance between batches is too much to allow a definite conclusion.

It’s confusing because of the way he presented data, but actually there’s no contradiction. (Jon thanks for the good find.)

I’ll list results that are common to all 3 tests:
1. Green more negative than purple: no contradiction here. Reddit poster’s result is –0.001, Djozz’s is –0.003, and mine is right in the middle –0.002. Coincidental or not they are actually remarkably close.
2. All 3 values are NOT that significant as far as effect on beam color (EDIT: wrong lol, as shown later, yes even 0.002 is a big difference) is concerned. Mainly because they are only third digit after decimal point and of low values (1,2,3).
3. In fact it seems so far ALL of the values listed for non-AR lens, no lens, green lens, purple lens, etc., are in the 0.001-0.003 range of each other (low value, third from decimal). Meaning this type of AR related tint mod is not going to change your beam color significantly.

IMvHO, outside of beamshot /white wall comparison, the best way to gauge Duv effect is to graph them on the BBL curve (NOT listing percentage like reddit’s poster). An example is pic below, where you could see a Duv change of 0.002 doesn’t alter beam color that much. I am actually very curious what the beamshot will show.

Thank you for the summary and sharing your perspective! I will add some of my thoughts...

I completely agree with Claim 1, and don't have enough info to comment much on Claims 2 and 3. I suspect that some really bad purple lenses I have incur a more than +0.003 shift, but don't have the equipment to tell. I might also add that the threshold for significance might depend on how tint-snobby someone is, and I personally find a change on the order of +/-0.003 very noticeable even without comparison, if the emitter is close to neutral.

I agree that there is no contradiction, but do maintain that there is inconsistency between batches. I am comparing the absolute-differences |Green - None| and |Purple - None|, and for the reddit data the green absolute change is greater, while from your tests the purple change is greater.

I do agree with you that plotting in color space is an excellent way to gauge duv, but I think the choice of 219B is suboptimal--I find the existing tint deviation of the 219B too large, on the order of 0.01. On that note, I would love to see plots of your 519A tests in color space!

I will respectfully argue that percentages are a very helpful way to gauge duv in practical terms. On a related note, I claim that the implicit question "is +0.003 duv significant?" is ill-posed without reference to the initial duv before the change. If an emitter starts off close to neutral, +0.003 would be a huge percentage of the existing deviation, and I feel many tint snobs will spot the difference. However, if an emitter starts off pure pink, +0.003 constitutes a very small percentage of existing deviation and would not result in a very noticeable difference: lots of pink plus a bit of green is still lots of pink.

I will go back to a previous analogy: is +10 lumens significant? Yes, if your light is currently off, which corresponds to an infinite-percentage increase. Arguably no, if your light is already at 1000lumens--I doubt many would notice the 1% increase.

Thank you for the thoughtful discussion. I will try to clarify and hope I don’t lose everyone. :person_facepalming: :slight_smile:

Sorry but your analogy of Duv with lumen doesn’t hold well, and I mention this only because it is related to the point I was trying to get across about reddit poster’s listing % change of Duv (no one does this I don’t think). Yes with lumen, percentage calculation is ok, because lumen is an amount. A LED with 1000 lumens has 100% more brightness than a LED with 500 lumens, etc… However, Duv is a number along a line on a curve graphed by x,y coordinates. There is no LED with negative lumen rating, but all LED’s have positive and negative Duv for this same reason.

I understand, but this is not quite true. A 0.003 change is the same change whether you are at 0.0001 Duv or 0.120 Duv. The pic below is my 219b 4500K with Duv –0.012, on which I’ve added additional Duv points. I hope it would make more sense than my writing.
One point is valid: I stand corrected and should have written: a 0.002 is a relatively small change, since “small” is so subjective, and small or not, a change in beam color has been noticed by various reviewers (see stephenk’s note above). Hope this helps to clarify & cheers.

This is an excellent point! My lumens analogy with duv is not an accurate one. Subjectively, however, I still find that the same duv difference is more pronounced when a source is close to neutral. I've played with the color space calculators from Waveform Lighting before, but thank you for introducing it anyways; it's an excellent resource.

After playing more with the calculators, I've created the following experiment for everyone to decide for themselves. It's not perfect, as the computer monitor does a poor job of recreating colors, but hopefully there is something to be observed. In the image below, all 4 sources are at 4500K CCT. Compare the top two squares, and then the bottom two. Try to decide: which pair has the greater difference in duv?

https://imgur.com/a/rI4SjH8

The duvs differences are about equal. (0.0098 for top, 0.01 for bottom)

@QR, I appreciate that you put a lot of thought (and “work”) into every post :+1: .

For anyone new to this and wondering what on earth we are talking about, if you like to try, Waveform Lighting calculator web site is HERE. It would get you “deeper” into the hobby and believe or not, A LOT OF FUN. Guaranteed lol.

The numbers come from this inexpensive device “Opple Light Master Version 3 (aka Pro)”. It’s the more expensive $40 item - do NOT get the cheaper Version 2. https://www.aliexpress.com/item/3256803116495145.html?albagn=888888&src=google&albch=search&acnt=479-062-3723&isdl=y&aff_short_key=UneMJZVf&albcp=15030837246&albag=127121838845&slnk=&trgt=dsa-42862830006&plac=&crea=555086564371&netw=g&device=c&mtctp=&memo1=&albbt=Google_7_search&aff_platform=google&landing=pay_0_user&gclid=CjwKCAjwgaeYBhBAEiwAvMgp2i-UDLyDk1SQXWNplGH0AhtwiyEQUNaFenyuto-UjZzPO5jRi0n_PxoCiScQAvD_BwE&gclsrc=aw.ds&gatewayAdapt=4itemAdapt

Just purchased the Opple Lightmaster 3 Pro. Look what you just made me do!

@stephenk lol coming from you I’ll take it as a compliment :+1: :slight_smile: .

stephenk has over 2000 posts...

and I just noticed his username.

Are you a fan of Stephen King perchance?

Beamshot of Convoy AR Green vs UCL AR Purple. Picture shot in RAW format with DSLR. Manual setting & WB @ 5000K. Both light and camera on tripod to minimize fluctuation. I noticed something that’s not frequently mentioned, that changing lenses not only affects Duv, but also shifts CCT about 50-100.

I hope you could see the UCL purple lens makes the scene more yellowish (attention to the white wall @ middle of the picture) but please keep in mind photography tends to exaggerate difference IMHO/experience. In real life use, I could see this difference against a white wall but it’s not as severe as this picture would indicate, and much harder to see when shining on darker subjects with colors instead of a white wall.

Even though this is comparison against a UCL AR Purple, not original Convoy AR Purple lens (I couldn’t find one to buy), I am glad that all my Convoy lenses have green reflection. :innocent: It does magically remove yellow tint from a scene.

Thank you for the wall beamshots, and for the enlightening discussion! The difference between the two seems pretty remarkable. Also very interesting observation about how CCT drops with increased duv--I suspect it's due to the fact that in the CIE 1931 color space, isotherms are not orthogonal to lines of constant duv. It's very strange that the CCT assigned to a point is NOT the closest point on the BBL by Euclidean distance--could someone explain why they made it so?

I also noticed how difficult it is for white to look white at warmer temps...neutral looks yellow-green, while -duv looks peachy or brown or skin-toned, there is just no white.

The nicest warm white I've ever seen came from some fridge bulbs, which are incandescent, heavily-frosted, and noticeably magenta instead of neutral--I'm not sure what filter they added to make them that way, but the tint is just pure awesome, with extremely good reds that beat any unfiltered incandescent and even my dedomed 519As. And it actually makes white things look white even at 3500ish K.

Has anyone seen the wide range of options available (219b, 519a, XPL HD, 8 emitter colours, 8 x different degree options) at flashlightbrand.com?

I came across it after watching a Weerapat Kiatdumrong review on a different light, but the size comparison was with the 21D which caught my interest.

There is a note re the driver differences:

“12A FET driver ,max output 12A,It is greatly affected by the battery voltage and internal resistance, and the current drops rapidly.

8A CC driver, constant current buck driver, As long as the battery voltage is greater than the LED VF value, the driver still maintains a high current output.In addition, the new 8A driver uses springs instead of copper posts.”

I would go for the lower amp driver anyway for less heat. It also sounds as though with the 8A driver uses a spring at the head, instead of a post - this also appeals to me; I’m considering something like this for a bike light / edc.

If I could ask some questions here, I’m guessing at some things without actually knowing:

1. I’m not sure I understand the “degree bead” options. This looks like a wide angle setup - what option would give the most throw here?
2. Being a flashlight Philistine I’m just after the best light to light things up; which would be the best emitter?
3. If I wasn’t a flashlight Philistine, which would be the favored 519a color (4500?)?

1. 10 is the narrowest beam, 60 is the widest. Even with the 10, it’s not exactly a throwy flashlight, though.
2. 519A has great brightness, tint, and CRI. Most other emitters only have two of the three.
3. That depends on your taste. 4500K is what I like, although 5000K is all right indoors too. You might like something way different, but 4500K is probably a safe starting point for a lot of people.

Thanks for that nicodimus22

I’m not sure if you have look around, short list and choose a S21D-a light with TIR for a bike light.

Or at some point, you are confuse while reading this thread.

Imho, take a look at the S12 triple emitter with 519A-8A driver. It’s more appropriate then the S21D for a bike light.

I will, thank you

I was thinking the same thing. Bike light probably has specific requirements such as certain brightness and not shining on eyes of people in opposite direction, etc., and the S21D with Nichia (lowish brightness and throw, no easy control of direction) is probably not the best candidate, as nutty as I am about it :slight_smile: .