Maybe? It's a stable measurement.
-Garry
I can’t remember where I saw it, but I think I recall some post on BLF where someone said the Vf of parallel emitters is normally lower than one emitter. Perhaps it is similar to the effect of putting resistors in parallel making a lower total resistance? Or maybe I’m just remembering that wrong, or I’m just stupid, or both! J)
I don't have time to look up the Vf chart, but wouldn't the current be split between the 2 emitters? So each would be receiving about half the current.
Yeah, but the batteries are wired 2S2P, so should be enough with a buck driver?
Maybe I mis read something. I thought Garry was asking about a low Vf reading accross the parallel emitters.
What I was saying is that I assumed the 2S2P battery pack would be more than sufficient for the three parallel emitters, so I thought that couldn’t be the reason for the low Vf. I stand a great chance of being wrong, however.
Yes. Sorry, I confused things about amperage. Yes, LED's are splitting that 1.89A, so 0.63A each. Of course the 0.57A splits to 0.19A. Still doesn't explain a 1.57v vF, does it?
-Garry
I don't think it is the reason for low vF (esp. since it handles high for 80 to 90 minutes just fine), but this battery pack is junk. Of the 4 cells, I believe 2 of them are "dummy" cells (measure 0.00v across each and are wired incorrectly for a proper 2S2P arrangement) leaving two cheap weak cells to handle the load. I've not tested the two working cells yet, but will. Actually maybe I'll try them on my SolarStorm X3 which pulls around 2.6A at 8.4v. I bet it won't handle that load well.
-Garry
Oh, I didn't catch that second pic. Wow, that is low. Don't know what to make of that.
I said 2 emitters above. Sorry meant 3 and 1/3 current. You obviously knew what I was trying today.
Which Ammeter did you get of the choices? Do you think they can actually take 50A and 100A? Seems like a real good deal.
There is definitely PWM because it shows in my camera. It doesn't look too bad in the camera (not as bad as others), and I don't notice it with my eyes.
-Garry
I went with the 30V, 10A red & blue display. I bought from US Seller NY Platform which I've dealt with before. See post #12 in this thread for more pics and my link. No idea what they can really handle. They do come with really thick leads which is nice to see!
-Garry
In my non flashlight experience, I would say it is due to the pwm. Ideally you would need to scope it to see what is going on.
I think the PWM guys above are correct. I just read in something unrelated that a typical DMM samples voltage readings at a pretty low rate (didn't specify rate) and average the readings. Not sure if that is true, but it sounds reasonable.
I would think it it would have to do with the PWM. Don’t forget your meter is set to DC. PWM is not really DC, it’s current being turned on and off very rapidly. Just because it always flows in only 1 direction doesn’t mean it’s the same as constant DC. The LED can tell the difference, doesn’t shine as bright, perhaps your meter “notices” that too and “thinks” that it is measuring a constant DC current, but at a lower voltage.
I would think that a more sophisticated meter could read the peak voltage of the pulses
Thanks guys! PWM explanation makes sense to me. One of these days I need to figure out how to measure PWM with my meter too.
-Garry
These little things are cheap and pretty useful. I’ve used it for monitoring vehicle bus networks etc, it should show driver pwm no problem.
Yeah, but can't I do it with my current meters which can measure Frequency and Duty Cycle? (Both my orange and green ones in the above pics have those settings.)
-Garry
“do it” - which it do you mean? Anyway the answer is probably no regardless of the question. 
Knowing the frequency or duty cycle doesn’t do you a lot of good when you can’t tell what the voltages during the “on” and “off” portions of the cycle are. You’d use a scope to see a trace which probably looks like 0v with a small spike every little while. The actual LED vF would be what’s going on during the “spike” (the ON portion of the cycle). You’d actually be able to see of that on a scope. Apply your imagination to the images in post #6 here.
Some drivers are able to maintain a smooth output with no PWM, even in low modes (the LDCH LD29 is an example). Those drivers would allow you to get a much more accurate reading with your DMM. Most drivers use PWM which ends up being visible on the output to the LED.
I always thought you need an analogue meter to measure the average voltage of PWM. Or put a capacitor in parallel to use a DMM.
lightme, the thing here is that the average voltage does not matter at all. It is simply not relevant. A very good average voltage and average current could be used to determine average “Power” (wattage), but you won’t learn things like LED Vf or other important info related to efficiency. As alluded to earlier, the LED just won’t light up at 1.5v - you’d get nothing. But the actual average voltage could be even lower, say around 1v or who knows?