With darkness upon us, MTBR does such a great job each year coming up with a difinitive testing procedure for lights. They have outdone themselves again with their newest updates.

Their lighting review are listed here: http://reviews.mtbr.com/blog/category/lights-shootout/

This year's update includes the use of a light meter and measuring ambient light bounced off a ceiling. 

You can find the info here http://reviews.mtbr.com/blog/lights-shootout-light-meter-measurements/