Red Leds: Is cree still the best option for flashlights?

According to the spreadsheet the Photo Red XP-G3 has a typical wavelength of 645nm and peak wavelength of 670nm. The XP-E2 only has a peak wavelength of 650nm listed. I’m confused again, which one is better in terms of tint? = more red.

Define: more red

The XP-G3 datasheet says:
Peak Wavelength Minimum: 650nm
Peak Wavelength Maximum: 670nm

Dominant Wavelength: 645nm

The range of peaks is listed, as I understand, because there can be variation between batches.

Peak is where wavelength with the highest intensity. I wasn’t aware dominant wavelength was a separate specification, but from a quick search, I guess the difference is peak is based strictly on spectral power density, but dominant sounds like it is in some manner a perceptual specification. I guess maybe it’s adjusted based on the human eye sensitivity to the wavelength that would appear identical from a true monochromatic source (color LED’s are close to monochromatic, but not quite).

The XP-E2 datasheet does not specify dominant wavelength. The peak wavelength minimum and maximum are the same as the XP-G3.

Both should appear basically the same.

Closer to the deep red wavelengths. The 620nm XP-E2 is indeed a bit orange-ish.

Thanks for the explanation. But XP-G3 has better parameters and should handle a bit more current. Maybe I’ll organise a small groupbuy (approx. 30 leds).

I see. In my perception (everyone differs a bit in how far red they see), at longer wavelenths than 660nm the colour of red does not change anymore and your eyes do get more and more insensitive for it. A good compromise I think is 640nm: looks very red and not orange, and you do not need bucketloads of output (as in: radiometric output) to be able to see something.

Hmm, so if the XP-G3 is slightly less into the far red wavelengths than the XP-E2 it’s actually good.

In my perception and opinion yes, but there is a sort of myth that the higher the wavelength, the better while in fact you are going to see less and less instead of a “redder” colour.
And there’s the hunters who like all sorts of colours for as many reasons as there are colours, but I do not know much about that.

Digi-Key lists 645nm for the XP-G3.
As soon as they will become available at mouser, roughly late july I’ll organise a small groupbuy 30-35 leds from them. Even with import taxes the price should be decent.

From Mouser for G bin of red XP-G3:

"End of Life: Scheduled for obsolescence and will be discontinued by the manufacturer."

Strange.

:+1: good idea, in for 5

Bump to see if anyone has tried one of the new xp-g3’s in photo red. I have enough photo red xp-e2 and xp-e’s, but wanted to see if anyone’s built a light with one yet? Was the group-by was ever organized? I’d be in. Thanks

Darnnit guys - you’re making me want to get teh gear to change out LEDs….

I wonder - would my .mil buddies like an IR FW3a?

How about a C8f Triple with the new red xp-g3’s? That’d be a killer hunting light, and easier to put a remote switch in the tail (I assume). I wonder if the output of the Xp-g3 is much more than a high-binned xp-e2 in red/photo-red. Obviously the xp-e2 throws better and can be de-domed if you wish instead of trying to slice the xp-g3, but hopefully the xp-g3 has a substantial increase in output. Interested to hear when someone gets their hands on one of these to test out.

I have tested the 660nm XP-G3 but have been too lazy to post the result sofar (=on my list). The output is really good, in lumen comparable to the 625nm XP-E2, but consider that your eyes, and the luxmeter, is 4 times less sensitive to 660nm than 625nm. The die is larger though so it is less throwy.

I built a light with the 660nm LH351H. I did not get measurements, but it definitely appeared competitive with other high-power red emitters when used in a Lumintop Tool AA, assuming you’re going for a deep red.

Hi Djozz.
Without posting your complete testing results for the xpg3 deep red LED. Can you speculate on a maximum (safe) drive current these LEDs can handle.
Just recieved some in the mail. Plan to build a couple lights. A S2+ single and a S2+ triple.

Thanks for all the info you’ve given this forum!
I already have several red and UV lights built based off your findings.

Sure, the max I found for the test led is 320 lumen at 3.8A, the more sensible setting I think is 260 lumen at 2.4A. Mind that to get 320 lumen at 660nm that is the same radiant power as 1280 lumen at 625nm. This is a very potent led.

Many thanks, this is helpful.

Bumping the thread to see if anyone has comments on the new Osram flat red, the sst-20 in deep red, etc… It seems like a lot more options for red Leds exists now since my original post

I did a test on the red flat, but never posted it (I’m in a sort of led test crisis atm). Unlike the green and white flat, the performance of the red flat is not special when comparing it to the Cree red leds. Only the illuminated area is a bit more even, which is a quality for use as a projection led but hardly relevant for flashlights.