Originally Posted by nitroRoo
I wouldnt rely on auto exposure. It depends on how your camera meter is set up (spot, partial, evaluative, etc) but if it sees more of the darkness, you're going to overexpose your light, and if it sees the bright spot of light, you're going to underexpose. I'd probably just manually set the exposure and view the LCD to get the scene as close as possible to what you see with your eyes.
Good point, I didn't think about what type of meter in the camera. All that can probably be acomplished is a comparison of lights to each other at one location.
Originally Posted by slvoid
Yeah just lock the exposure or manually set it. All you want to do is get a good idea of how much wider a beam is compared to another one and how much farther it is.
Or if you want an absolute value without comparing one light to another, use a light meter.
OK, that's what I thought. I think the photo is actually better info. for a person trying to select a light.