EV, without an ISO reference
most photographic discussions assume ISO 100 so the EV concept can be applied to real-world situations
I guess most photo discussions don't include folks who grew up using the EV system.....
When I see EV -2, I consider that to be the real EV -2, not a luminance value.
I find it strange that Canon chooses use the EV system for a function that is subject neither to shutter speed, or ISO. Its not like you could manually bump either of those and have the camera suddenly start focusing. Or, put another way, if you had the camera set to EV -5 things would call apart with focus, if the light were adequate.
My little peeve is when people say "it was so bright, it must have been EV 20 out...." or "it was EV -5, I couldn't see a thing" - neither of which is related to any brightness.
Too old school I guess....