Oh and by the way, wow, that Vf is linear. I'm thinking using about an 0.8 ohm 2 watt fixed resistor and a FET would maybe work pretty great as a near (but safe) direct driver. In other words just use any direct driver and heat sink a resistor on the led lead onto the case.
The lux meter is always relevant, in regards especially to how it samples the light spectrum. I suspect for high bin led's this could maybe explain the high readings.
Actually I doubt that, in my testing an XP-L HI is lucky to even match 1300 lumens. Highest I have seen so far a bit over 1200 lumens, usually closer to 1100-1200.
Which actually makes sense. Maxed out XP-L V6 models are generally around 1600-1700 lumens. The V2 is 28% lower flux bin, so thus by the math it should put out around 1200 lumens all else being equal.
Assuming we have an accurate lux meter, a potential advantage of this method is it might be easier to measure the absolute output without needing to calibrate the apparatus.
Texas_Ace, are those LED lumens or OTF lumens?
OTF lumens for the most part, although I have not measured a known good HI model without a light yet.
Although it should be 28% lower then the V6 which seems to max out around 1700-1800 even at the emitter from others tests.
Based on measurements I’ve done, the XHP35 HI measured is closer to the dedomed XPL V6 1A in throw than most XPL HI V2 tints.
In an EE X6, I measured 70Kcd with a XPL HI V2 3B and 94Kcd with a dedomed XPL V6 1A. This was at direct drive currents with a 30Q cell, about 5.5A and 6A, respectively. With the X6’s reflector area of ~630mm^2, the effective luminances of the LEDs are 111 and 149 cd/mm^2, respectively.
Using the method in the OP I measured the luminance of the dedomed XPL V6 1A at 5.5A to be 141 cd/mm^2, which is consistent with the measurement in the X6. The XHP35 measured had a luminance of up to 135 cd/mm^2, which is significantly higher than the XPL HI V2 3B. The XPL V2 1A is another story though; I’ve measured it to be ~20% higher in lux than other V2 tints, but it has a noticeable bluish tint.
In an unrelated topic the results from my build on the MaxToch Shooter 2X came up, thought the actual numbers from that might be relevant here.
This is copied and pasted out of robocop’s thread on the Shooter 2X…
“I took some measurements of voltage and amperage at the the emitter , and when I put the bezel/reflector back in it went on a little differently. So I checked lux again and got a surprise! 326.25Kcd for 1142.37M throw. Pretty much where the de-domed XM-L2 started out but with considerably more lumens. Sweet!
0.06A at 10.80V for ~89 lumens
0.55A at 12.22V for ~783 lumens
2.87A at 14.75V for ~2346 lumens
She’s singing along nicely!
And the LD-2 driver is very efficient apparently, with tail current readings at .06, .57 and 2.89A earlier (cells were higher charged then)”
(edit: used a clamp meter with a loop of wire between the negative lead and mcpcb for amperage, direct readout from the mcpcb for voltage, in the light)