On Mon, 24 Mar 2008 08:34:04 -0400, Jack Erbes
wrote:

you'll find that those will intrude on your
night vision some even at the dimmest settings that lets them be useful.

Has next to nothing to do with night vision. Same thing is true in
broad daylight. When you have a relatively bright light shining
directly into your eyes it is more difficult to see dimmer objects.
Regardless of the actual ammount of light involved. It takes as much
as 45 minutes in close to complete darkness to get full night vision.
Ask any astronomer.

Casady