GB 351D closed.

BlueSwordM, that’s interesting. That’s not what I’ve observed. Maybe there are certain batches on the market with below the BBL tint but I haven’t seen any. Can you post a test showing the negative duv? That would be beneficial to alot of people here who like the performance of this emitter but don’t like the above the BBL tint.

It’s at least right on it at 3A (Maukka posted his measurements here). The tint change is very obvious as you increase/decrease the current.

Djozz’s measurement of a single shaved LED only tells us what is possible with some samples of this LED. It doesn’t show us if there is an effect (tint shift) that can be expected with all samples.

Aha, three stages slicing.
Thanks for the tip. :+1:

I can confirm though, that the tint of this LED gets warmer and seemingly more to the red side when you slice the dome.
Very nice result here too. Bit of a messy slice though, but under a TIR you won’t notice that.

I've sliced some XHP50A emitters, at ≈1.1mm without sanding too as it kills the bond wires rather easily. In 3 or 4 slice bites from different angles. Of course ends up looking a bit messy, but that is unnoticeable even below an aspheric at focal lenght distance “batsignal” :-D mode. I do notice slight barrel distortion at the emitter projection edges and dome remainings, but looks good other than that. I like the result of this method, there's noticeable intensity gain and probably the output loss is not as dramatic as with more radical dedoming ways.

Cheers :-)

Guys, has anyone made the output test of these 351D 5000K 90cri? I would like to use with C8f 21700 and I want to know what can I expect.

You can count on 1000 lumen at 3 Amperes per LED.

Yep.

However, I would not overdrive the LED too much.

The 90CRI variants tend to draw quite a bit more current than the 70CRI.

Because of this, efficiency drops quicker as you push the LED harder, and the LED ends up in its inefficient point of luminosity sooner.

maukka did, but did not mention it in the thread title, colour test in post4, output test in post7: Samsung LH351D color testing - #4 by maukka

I wonder what a 5000k 90cri dedomed would do? If it would shift the same way but maybe 4200K?
I have several of the 5000k 90cri leds bought from the Arrow electronics deal, but I have no way to test them.

I have no idea what it does, dedoming/slicing is like magic. Only rule that I gathered over the years is that dedoming high CRI leds always returned nice tints.

Only one way to find out. :smiley:
How about if I send you a couple to test?

I think I have some of those, it mainly requires doing it and that what I do and don’t do in my hobby is quite random. And unlike in my work, no-one corrects me :person_facepalming:

Please add 4 more for me, I already asked for 6 but I’d like to buy 4 more if possible

What I did do:

(perhaps this is not the right thread for this, but I already started it here, sorry about that)

I sliced the 4 LH351D 4000K 90CRI leds in my SP36 sample, and took some measurement before and after.

The sliced leds in reflected light show that I sliced very close to the phosfor, on many area’s all silicone is gone on top of the phosfor layer (and perhaps a tiny bit of phosfor too but that does not show up when looked at the lighted leds)

I should also have done tint tests before the mod, but I forgot them :person_facepalming: . So the tint results before slicing will be represented by the hotspot of a Q8 that I have that has the same leds, that should be similar.

Hotspot of Q8 with intact leds, low 7135 under 350mA current (so under 90mA per led):

Hotspot of Q8 with intact leds, highest FET current (over 4A per led):

Hotspot of SP36 with sliced leds, low 7135 under 350mA current:

Hotspot of SP36 with sliced leds, highest FET setting:

Here’s the beam of the Q8 with intact leds compared to the SP36 with sliced leds next to each other on a white wall. Phone camera white balance set to sunlight, the tints are not completely accurate to reality, but you get an idea. The tint difference is larger in reality than in this picture.

In my own experience the tint went from ok but not really nice (unsliced) to super-nice, rosy and not yellow, nice both at low and high current. The tint improvement is larger than the tint/CRI data suggest.

I did notice some slight rings in the beam after slicing the leds but that is a SP36 thing, has nothing to do with the leds. It may even be just present in the prototype SP36 that I have.

Now for the output loss, I did measure that before and after. As I noticed before in other mods with it, after slicing the 4000K 90CRI LH351D, I lost a lot of output, more than with an oldschool Cree dedome.

Measurements with fully charged 30Q’s.

Before slicing: 3seconds 4250lm, 30 seconds 3940lm
After slicing : 3seconds 3490lm, 30 seconds 3235lm

So the loss is 18% compared to before slicing. One must suffer for getting the perfect tint :slight_smile:

The final cost of changing the SP36 from 70CRI cool white with tint shift in the beam (the stock XP-L2 leds, about as bright as this host can go) to 93CRI 3500K with no tint shift in the beam (the sliced LH351D 4000K 90CRI leds) is 34% light loss. For me that is an ok price payed.

Thanks djozz, quite enlightening shaved dome tint and CRI study for high CRI emitters. It is quite pleasing to see it actually enhances CRI a little bit :-) further. Now I understand why my sliced SK98 XHP50A 4000K CRI90+ looks noticeably warmer than a 4000K emitter in reflector. I like this. I also have another sliced XHP50A 3500K CRI90+ G4 flux bin waiting for action, it's gonna look warm and cozy. :))

Cheers :-)

34% light loss? Since our eyes and brains do not perceive the different visible light spectrum frequencies with equal sensitive one could also say those low CRI emitters are “gamed” as more energy is invested in the frequencies we are more sensitive to, something which can be seen as a sort of cheat which inflates the lumen figures.

I can pleasingly deal with such “loss”. :-D

Cheers :-)

What the loss of output for Cree dedome?
I always assume the loss should be like xpl hd -xpl hi differences. ~3 bin or ~20%.

The few times that I measured it (old type cool 70 CRI Cree XP-E2, XP-G2 and XM-L2), the light loss was close to 10% for a clean dedome. But it may vary, I only measured it a few times.

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: