Hi!
So i just bought a Ultrafire f13 from gearbest at 9.99 with a coupon.
I was wondering if i should do a led swap (xm-l u2 included) to a xm-l2 u2 or the diference is neglectable.
Thank you!
Pics from Match’s emitter test threads.
These are the output numbers you’ll get from the respective emitter on copper or aluminum (stock) stars at certain drive currents.
The final results depend on what your driver is doing, and the type of star/mcpcb you use.
You’re probably looking at 100lm difference if you stick with the aluminum star and don’t mess with the driver, copper wont make much difference in this case. 100lm is cool on paper, but unless you took a picture before and after you wont be thinking “that is noticeably brighter”.
If you switch/tweak the driver (I cant recall what people were getting by tweaking the driver) to lets say 4A, and you have a battery capable of that current then you’re looking at 500/700lm (Alu/Cop) difference. Definitely noticeable and a before and after picture will be amazing. 
Keep in mind these are just rough numbers, there are tons of variables involved.
Unless you are changing to an led on a copper star it seems a bother for very little realized gain.
On the F13, I’d just go with a couple of mods, e.g.: