LED test / review Osram SYNIOS P2720 DMLQ31.SG white - Small chip, but big in luminance - at low current!

It’s very unfortunate that you started doing these luminance measurements just as these new LEDs started appearing.

This LEDs are on sale at least for over two and a half years (begin mass prod. Apr 15). I don't know if these emitters were already mentioned in flashlight forums.

Maybe it is better that other members doing these luminance measurements. In most cases my values seems to be wrong. I am not sure to take newly this risk for updating the luminance values because they could also be wrong for any reason.

Well yes, but we didn’t know about them.

I think you should continue ;).

As the frontier of luminance testing you stumble upon problems. That’s expected. Please don’t give up, luminance is just as important as total output.

Both me and koef made the same mistake when measuring the synios.
I only found out that we had a flaw in our testing method after three people used synios LEDs and got bad results in their flashlights.

Fortunately this is just for the synios LEDs, all other LEDs are fine and the results are still correct :slight_smile:

Actually many LEDs will have a problem with this method of calculating luminance. Any light that you see not coming from the die itself will inflate the calculated luminance. To name a few: XPG3, XPL2, luxeon V, nichia 219C, XHP50.2, XHP70.2.

That being said I find koef3’s detailed pictures and measurements to be very useful. But for the luminance measurement I think a careful in-flashlight test will give a more accurate result.

Yes,

Koef3 tests are very very good.

Final word about the certain led should be given in practical use. It can have all numbers in a world but when I “throw it” to light meter that is truly real state of matter.

Are you sure about the 219C?

Yes, I measured the bare die luminance of the 219C and observed the in-flashlight results were much less. This was before I discovered this stray light effect in my investigation of the XPG3, so I didn’t understand the discrepancy then. But if you look at the dedomed 219C the white area around the die is significantly lit.

In my led surgeries it appeared that the 219C is different from the old Cree leds like XP-G2 in that the phosfor is not a compact rigid layer right on top of the light emitting surface, but a layer of phosfor mixed silicone that is inside a white-coloured shallow square cup surrounding the die. On top of that I assume that it is a flip chip design so the light does not enter the phosfor containing layer directly, but passes the die base first.

Did you post these results anywhere?
I have been thinking about tuning my Noctigon Meteor with dedomed 219Cs. It currently has de-domed 219Bs.

Some 219C measurements:

I measured 300Kcd at 5.5A in a UF1504, which has a 3019 mm^2 lens.

Thanks, I used your numbers to determine the luminance of the 219C D240 (R9050) shaved at 2A: 41.8cd/mm^2. With 12 of these and
UCLp lens the Meteor should do 34kcd. Thats not too bad. The 219Bs do 20kcd with dome and are probably similar without. I really like the beam profile and throw, but higher efficiency would be really nice (especially less heat!).

Using your calculations I get peak 154 cd/lm for D320.
Assuming current-handling of 219D is the same (yes, I know how good this assumption is), it should do 210 cd/lm 195 cd/lm in D340 bin. This number may be way off, but I believe 219D is worth testing. :wink:

Why should cd/lm be higher with the new LED? It’s probably the same or worse.

See Product Data LED | NICHIA CORPORATION and Product Data LED | NICHIA CORPORATION
They state “Luminous Intensity”.
Also, you can see a smaller die on the photo.

Thanks! I didn’t notice that before. That’s seems to be quite a nice upgrade! The brightness increase (3.7%) is negligible though.

Is that taking into account the clear aperture of the lens?
Lenses usually have 95% CA, or even less for cheaper quality ones.
The outside circumference is not very aspherical and therefore may not contribute to the lux in the spot.
The best way of being sure is putting a circle of paper or metal in front of the lens which has a smaller diameter than the lens, in order to ensure you’re only calculating lux and area for the clear aperture.

Based on looking into the front of the lens from a distance, nearly the full 62mm diameter is active. This area estimation seems to give a consistent measure of the dedomed xpg2 luminance at 510Kcd at 4ish amps.

:+1: