Mugsy,
there has been discussions on here about a helmet with a chin activated filter glass. It seems to be pretty popular. I think that the name is Accu-Strike and on their website they have a video that shows how it works.
I use a Lincoln helmet with the self darkening range of 9 to 13. I use it on about 10 and I like that. If I accidently position my head so it blocks the sensor, even though it doesn't trigger, I don't get any flash burn problems. The lense is dark enough at the start to stop harm to the eyes.
