testing a red XP-E, and comparing it to a red XR-C, 22/4/'14: XP-E2 results added in post #32

Thanks for posting your results djozz. Good work.

BTW, your lumen numbers are probably bogus. Lumen numbers are done by weighting light output by the human eye response curve. Your lumen conversion constant was probably derived from measurements of white LEDs. Lux meter readings are also weighted by eye response, but the conversion constant will probably be different for colored and white light.

Comparing your red “lumen” numbers between the LEDs should give a reasonable idea of their relative outputs, though.

Which way would you expect the results to be skewed?

I suspect that the true lumen numbers will be lower. Or maybe higher.

Fair enough.

Visually the red lights appear brighter to me than their lumen numbers suggest.

If anyone has amber to try, I’m always interested in those (for “low/no blue light” use in evening hours)

I give the lux/lumen readings to compare with other leds that are similar in colour, in that relative aspect it is useful , and although it may not be the absolute correct number for all single colour emitters, it does say something of how bright it is perceived (not completely 'bogus' IMO, but a little: yes). I know that it is much to ask of a cheap lux-meter to use the right correction curve so that for all measured wavelengths it is correct for the human perceived brightness (although it would be a simple software correction, I wonder if it is done right, or at all).

1 Thank

Is it not safe to assume that all colors of XP-E are improved over their XR-C counterparts?

I must correct myself: I assume that light detection in a luxmeter is done with a single detection device. If it does not have the correct sensitivity for different wavelengths, according to the definition of the lux (not likely), any sensitivity correction must be done by optical filters before the light reaches the detector, after the detector the luxmeter does of course not know which part of the signal comes from which colour of light. For 24dollars shipped there's no way my luxmeter has such pre-detector correction (if it exists at all).

Pretty much all lux meters have a silicon photodiode sensor with a greenish filter in front of them. The filter is supposed to match the diode response to the human eye response.

The quality of that filter/match varies quite a bit. If you are looking at wide bandwidth white light, differences in wavelength/output tend to average out. Looking at a narrow band light (like a red LED) has greater potential for a mismatch at that wavelength being significant.

Nice to see that they survived that much current, as my red XP-E SK58 gets too hot to hold (on a 14500).

any news about xp-e2 red?

Well, MRsDNF has bought some red xpe2's for me from Cutter , and sent them to me (he even refused payment ), I got them in last week and will do a test one of these days :-)

that’s nice,thanks both of you.

I have a few customers who have lights with the XP-E and now some with the highest binned XP-E2 I could find. They both told me that they feel like the lights are visually more than 10% brighter with the XP-E2 vs. the XP-E. This is just anecdotal but cool to see that they can tell a difference.

I ordered a Philips Rebel ES 660nm Deep Red LED, as discussed in another thread. Probably not as bright but redder.

Rmm at 1.9a would the red xpe2 make a Roche f12 get hot on high quickly? Or a tank007 e09?

I did the red XP-E2 (630nm) test (with big thanks to MRsDNF who sent me a few leds for free, coming from Cutter), above stereo-picture is after the testing. I also re-tested the red XP-E because it was sitting there reflowed on the Noctigon already, and I wanted to re-check everything, now that I use a new power supply. Below are the results. BTW: the XP-E results match reasonably the former results of that same led in the OP, so my two (both lineair) power supplies more or less agree on their current measurement (jay!).

So, another improvement over the the XP-E, although the Vf of the XP-E2 seems to have raised, compared to the XP-E.

But, although I think what I see is mostly the real difference between XP-E and XP-E2, also keep in mind that the XP-E was an unknown bin bought from Fasttech, and the XP-E2 was the top P3 bin bought from Cutter. (EDIT: the Cree tool mentions there is a P4 bin, but Cutter's bin is P3)

Wow, that’s an impressive difference, even considering that it’s an unknown bin XP-E vs top bin XP-E2. It is fortunate that it started with such a low Vf. I can’t see the higher Vf being an issue for running a single emitter on a single li-ion.

Great work!