Thanks Mr T Bear,
But then flashlights are used in the "real" World so "rough" "ball-park" "guesstimates" are maybe of more use.
That's why comparison(s) between several flashlights are usually better because external factors get in the way (such as ambient lighting, your eyesight & dark adaptedness. etc)
Maybe:
In as dark as area as you can get. How far away can you see a person? How far way can you identify their face?
My eye sight is not very good. I don't often have stereo-vision (I have a very lazy eye) but I think I have quite good night eyes. Or not. That's one of the reasons why I use SureFires cos they help by providing the best possible light.
Don't let me near a firearm cos although I have pretty steady hands, my aim is not very good. Not that I've ever practiced. I'm a bit of an unco!
Al