BLF member rngwn sent me two of these interesting 7070 leds for testing. He found them on alibaba and asked for a few very high CRI samples. Depending on the performance he will order a batch of these and sell them to BLF members.
I did not get the manufacturer's name, or a datasheet, just the typenr GT-FC40, and that they are 12V, 5000K, and very high CRI.
Appearance
First how does the led look? It is clearly a 16 die led (4 strings parallel of 4 dies in series, I assume), but very tightly packed so it may produce a good beam in smooth optics, just like the XHP35.Here is a picture at 1 mA, to show the emitting area.
Not all dies show the exact same emitting colour. This is not because of the very low current, at 1A the same colour variation can be seen. Also, see the top pictures, there are some specs of dirt in the led, they are not on top but mixed in the phosfor. I hope that production batches do not have that, but at least the performance does not seem to suffer, as seen below. All in all production control seems not perfect.
Tint
I measured the tint of both samples at 1A, straight above the led, and at 60 degrees. Then I placed a small smooth reflector on top of led nr. 2 and measured 3 positions in the beam: middle of the hotspot, the corona, and the spill. Here is the tint data of the hotspot from the smooth reflector:
The beam looks really good by the way. No obvious ugly tint shifts, just a mild peachy corona. Here's the beam of led nr2 at 1A through the smooth reflector, projected on the ceiling, underexposed to show the profile best. That looks very pretty I think!
7 measurements is too many to show all the graphs, so here is a summary of the tint data in table-form.
CCT | CRI | R9 | duv | |
led 1 bare, straight above LES | 5340 | 95.5 | 93.8 | -0.0035 |
led 1 bare, at 60 degrees | 5080 | 94.6 | 85.2 | -0.0007 |
led 2 bare, straight above LES | 5410 | 95.6 | 97.8 | -0.0049 |
led 2 bare, at 60 degrees | 5150 | 95.1 | 90.6 | -0.0023 |
led 2 in smooth reflector, center hotpot | 6220 | 94.9 | 92.4 | -0.0023 |
led 2 in smooth reflector, corona | 4780 | 95.6 | 90.6 | -0.0018 |
led 2 in smooth reflector, spill | 5248 | 95.6 | 93.7 | -0.0035 |
Now that looks like the manufacturer delivered what was asked for, a solid 95 CRI in both leds at various circumstances, and everything close to but below the BBL. No complaining here.
Output performance
This is a 12V led, but the best comparison is with a XHP70, with dome ibtact, it more or less shares the same die-area.
So in the graph I added my only, pretty old, test data of a XHP70 led, a N2 bin led while a modern XHP70.2 led is at bin P2 which is 3 bins more output. Nevertheles it will give an impression where this led fits in. Mind the voltages btw, the tested XHP70 is a 6V led so not 1 to 1 comparable that to the 12V FC40.
It looks like the FC40 leds perform similar to the old XHP70 at the same current, but at double the voltage, so almost twice the wattage / (a bit more than) half the efficiency. The lower efficiency is normal from a 95 CRI led, but I am pleasantly surprised by the power handling of this led (at 7A it ran at 92W for a few minutes), and the top output of over 4500 lumen (although I would drive this led at maximum 4.5 A / 3500 lumen)
Conclusion
I like this led, it looks good, gives a good beam, has great CRI and has ok efficiency for this great tint..But it is 12V, so not easy to drive. A 4A 12V driver is not common, big and also expensive, so it is a bit exclusive to use this led in a flashlight build. I hope that rngwn manages to have the manufacturer a 6V version built, or even 3V !