How to measure Vf?

[kosPap]

well it seems I am progressing from making workable mods to better performing ones...

at this point I want to remove the individual LEDvariance in performance from my builds (mainly drp-ins0

So....is there a simple way to measure the performace/Vf of a LED and sort them?

Like connecting DD each one in a 18650 and measuring Adraw...that seems the simplest and most relevant way to actual performance...

(in simpler terms I want to know which of those Q5 I have have lower Vf, thus a more promising performace ability)(Next comes tint check)

Probably I am missing a lot though...your enlightment is needed

 

[Th232]

If you're fine with connecting them up, I'd just hook it up to a constant current source of some sort, run it and use a meter to find Vf across the LED. If my understanding is right, an LED A with a lower Vf at 350 mA than an LED B will still have the lower Vf when both are run at 700 mA.