As these LEDs were tested in free air, actual results may vary significantly in other applications such as encapsulation/enclosure and closer to a heat source such as a driver circuit and other LEDs.
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BEAM SHOTS - LCK26K vs NichiaCS

Some Nichia (NSPW500CS - Color B Intensity U) LEDs were compared to some 26K LEDs (ebay 26K). The beamshot comparison setup was three CR2016 button cells in series with the two LEDs connected in series to ensure they got the same current. The output level was quite similar (perhaps a slight edge to the Nichias in center spot brightness) but I preferred the color of the 26Ks. The 26Ks seemed a more uniform white color and the Nichias had a blue center with a yellow ring.


Pre Burn-in comparisons
The first set of pictures are some pre burn-in comparisons against some known lights.



Before and After Burn-in
This next one is a side-by-side comparison of the LCK and Nichia LEDs before and after burn-in for 147hrs at 57mA. Note that at 57mA the LCK was run at almost 3x rated current compared to 2x for the Nichia. The reason I selected this current is that it is close to ArcAAA current (approx 45-55mA).


After doing a quite a few other tests on the Nichias - the one I grabbed to test as a fresh one was either quite a poor performer or I didn't take a very good Lux reading (probably the latter ). A fresh Nichia's output at this current should be in the range of 43-52 Lux. SEE BELOW FOR A LUMEN MAINTENANCE PLOT ON THE NICHIA CS. The Nichia's output only dropped 15% after 145hrs at 60 mA!


LUMEN MAINTENANCE: LCK 26K at 30/41mA
Because I pushed the LCK 26K LED so hard in the previous test, I ran another couple of tests on fresh LEDs to determine what a "safe" operating current would be. The LCK 26Ks look fairly stable at 30mA. Some of the variances/measuring error could be due to ambient light in the room, searching for the "hot spot", and changes in ambient temperature. Output drop is 8.8% after 48hrs continuous running. Good drive level for a flashlight but not great for a lantern or nightlight. It appears that 2x rated drive current is a little too much for the LCKs as well. There's a 35.5% drop in output after 48hrs at 41mA.




LUMEN MAINTENANCE: MJLED at 75/105mA
An uncut MJLED was tested at 105 and 75 mA. The results started out looking very promising but went downhill fast at 105mA. The data looks good for 75mA - there has been no noticeable degradation. Here's the graph:





LUMEN MAINTENANCE: LCK 10mm 65K at 20/30/40mA
Here are the results of the 20, 30 and 40 mA burn-ins of the LCK 10mm 65Kmcd LEDs. These LEDs have a published maximum forward current spec of 30mA, so I started them with a "relatively mild" overdrive of 40mA. After seeing the results I did another run at 30mA. After seeing those results, I tried 20mA.

The chart can be read as percent of starting brightness measured at 1 meter.





LUMEN MAINTENANCE: Ebay LoV 5mm 35K at 30 and 50 mA
Light of Victory (LoV) 5mm 35Kmcd LEDs were tested at 30 and 50mA. It looks like 30mA is a relatively safe drive level. Things go downhill quickly at 50mA - do not use these in your Arc or Dorcy if you value longevity. The epoxy lenses on these LEDs are not tapered like the Nichias.




SPOT OUTPUT COMPARISONS - VARIOUS CURRENTS
This is an output test (Lux at 1 meter) of various LEDs. (the legend is stacked according to the plot lines - top to bottom). I ran the three LEDs from about 12 to 70 mA and continued up to 105 mA for the MJLED.

These numbers are for spot intensity at 1 meter and do not represent total output. The beam width is narrower for the LCK and Nichia LEDs (and much narrower for the 10mm LED) so they give higher spot readings, however, my impression was that the MJLED gave more overall output at the same current. In addition, consideration must be given for the small sample set.

This has been presented many times before, but here is my version. It is fairly well known that LEDs do not maintain a constant Lumens/Watt output across the range of drive currents.

The chart reads as percentage of rated current output vs percentage of rated current. Confused yet? The 100% mark is at the "rated" current for each LED. I placed a linear diagonal line to show what a linear relationship would look like. Brightness is not directly proportional to the current.

For example:

When the Nichia LED is run at 12mA (40% of rated current) its 48% as bright as when run at rated current. In other words, when the current dropped 60%, brightness only dropped 52%.

Also, when the Nichia current was double the rated current (200%) the brightness only 163% of the rated current brightness.




VOLTAGE vs CURRENT (Vf vs If) - VARIOUS LEDs
Here is a sample of a few Voltage vs Current plots. This illustrates how careful you must be when driving LEDs with a voltage source.

Here is a Vf vs If plot of a LuxV(VX1U), LuxIII(SX1K), and a 1W Cree (non-XR). The second plot includes a MJLED compared to the SX1K and the Cree.




I did another run of spot outputs for the group of LEDs and included a couple of BS series Nichia LEDs that I removed from ArcAAA heads. I have plotted the output compared to the newer CS series in two tint flavours (B12 and C). I do not know how much the ArcAAAs were used that the BS LEDs came out of. The CS LEDS were fresh.





LUMEN MAINTENANCE: Peak Snow 29 at 30 and 40 mA





LUMEN MAINTENANCE: Nichia CS (CU) at 60 mA




If vs Vf Various LEDs (FoxUV added)




FoxUV Vf plot of 20 LEDs at 20mA