Thanks Denny. I appreciate the answers. Maybe I'm over thinking this and I'm not trying to be a PIA, but I'm thinking about the physiology of the eye and the physics of light. Light passes thru the opening in the pupil and is projected on to the back of the eye, the retina. In a flash injury, too bright a light comes in contact with the retina and burns it. A pupil could not constrict fast enough to prevent it, nor could it constrict enough to compensate for the extreme brightness. An auto dark would need to block the flash before it could reach the retina. Maybe I'm full of it but it would seem to me that would need to be the speed of light. The speed of light is defined as how long it takes for light to reach from the sun to the earth. That's about 90 million miles away. It turns out that the speed of light is 186,00 miles per second. I don't really want to do the math here but intuitively, if you were to set up the equation at say two feet, that auto dark lens would need to react in an increment of time that is almost immeasurable.
