GB 351D closed.

I remember some measurements from fonarevka, there was about 20% loss for xml2

I can not find back my numbers on the XP-G2 and XM-L2 (I never managed a good dedome of the XP-L) but here is what I found for the XP-E2, it was even a bit less than 10% for these two leds:

Interesting,thanks. It is effectt of geometric optics, maybe it depends of die dimensions.

Thanks djozz!
Where these Samsungs all from AEDs first sale?

The Samsungs from the Q8 were from AEDeā€™s first sale, but the sliced ones from the SP36 were recently bought from led4power. I should have mentioned that, but I did not see an obvious difference in tint between those two sources (I know because when I bought the l4p ones I hoped that he had sourced a batch with a tint closer to the BBL, but it was clearly not so but instead very similar)

I did not test the slicing of that exact led (I could not find my stash) but I did try it on the 5000K 90CRI LH351C, the SPHWHTL3D50GE4RTMF to be exact, that maukka did extensive testing on (link). The effect of slicing this led should be similar to slicing the 5000K 90CRI LH351D though.

I now did my homework and did do the tint measurements before the slicing too.
I modded a Utorch S2+ clone with the SPHWHTL3D50GE4RTMF, and with a 2.8 A biscotti driver. All tint measurement were done in the hotspot (which is the most relevant part of the beam that you want data of).

First with intact led at 2.75A

Then I sliced the led, not the cleanest slice but Iā€™m beginning to suspect that how close you are to the die has more impact on the led behaviour than how even your surface is.

Now with sliced led at 2.75A

Same sliced led at 20mA (not from biscotti driver but by connecting the flashlight head to a led tester, so not PWM-ed)

Now apart from the colour data, that show a very similar effect as the slicing of the 4000K version (lower colour temperature, preservation of CRI, closer to the BBL), the beam looks like a very good neutral tint: no green, not too yellow, not too rosy, I like to call good coloured neutral tints ā€œbrownishā€. Here is a beam shot for an impression, all lights are at fairly low level, the sliced LH351C beam is in between a (led=intact) LH351D 4000K 90 CRI beam (Q8), and a 219B 4500K R9080 (ROT66, beam from TIR optic).

(the Q8 is a bit too green, the ROT66 is a bit too red, the picture shows less tint difference than reality)

I also measured the light loss from the slicing of the led and I now got ā€“19%, so that is also similar to slicing the other Samsung led.

One thing not mentioned before: slicing causes better tint and less light, but of course it also decreases the spot size of your beam and increases throw (did not measure by how much, my educated guess is 35ā€“40). This can be relevant to what flashlight you are building.

Thanks a lot for these efforts djozz.

If you feel like it, you could also do some staged slicing measurements in some other emitter. I mean, to see how does it compares a not so close slicing versus a close one with regards to output, hotspot size, temperature and CRI. Should be a gradual regression/progression in those parameters, I believe.

Cheers :-)

Yes, that will be interesting too. So many options for testingā€¦
Tomorrow my work week starts again, little chance for testing then.

Thanks for the tests djozz! Looks like there will be some Samsung shaving in my future.

djozz, could you give a link to technology of such dedoming ? Want to try it too.

Thanks for the testing Djozz. Now we know :+1: :wink: .
Iā€™ll definitely try a dedome in the next mod or two I do. 4300k is right up my alley.

Thanks djozz, this is very helpful information and makes me happy that I put this LED into my headlamp.

Will surface be smooth enough after this?

Yes if you use a new one. Some people use very fine sandpaper to polish it but iā€™m not sure anyone has proven that to be of any benefit and it can even be harmful if bond wires are involved.

Try one partial slice as a test, itā€™s generally very smooth. Then, go for a deeper second cut.

Edit: this is probably obvious but you want to make sure itā€™s soldered to an MCPCB so you have something to securely hold it. You can use a flat washer over the top as a guide if you can get it to the right height or just freehand it.

Iā€™m interested in LH351B 2200K and 3000K. 6 of each.

Thanks for the information.

PM was sent

If someone still interesting in 351D 4000K 90cri 40pcs are available)

I am waiting for the LH351D 5000K 90CRI to arrive at you :slight_smile:

I would be very happy, if I could see spectral/CRI measurement before I will buy them. If results are promising, I might exceed my initial interest numbers.

I can remember, that you have (or you did have) LH351B 2200K of two different performance bins. What is your current stock of them?

Managed to put LH351B 2200K in my EagleEyes X1R. I really like them warm CCTs. Quick photos with my smartphone (WB Daylight).

Left to Right: EE X1R (219C 2700K), EE X1R (LH351B 2200K), OTR M3 Pro (Nichia E21A 2000K). All with TIR Optics.

Not visible in the photo but 351B 2200K definitely warmer than 219C 2700K in real life. But still not as warm as I wanted it to be. Candle like E21A 2000K still my favorite of the bunch.

Left to Right: Cricket knockoff lighter in TURBO, OTR M3 Pro E21A 2000K + diffuser, EE X1R LH351B 2200K + diffuser

Thanks AEDe.