IMO auto darkening lenses are the worst you could use. If you read the fine print you will see that the auto lenses can in no way operate fast enough to protect your eyes as good as the regular lenses. Your eyes get a very small amount of flash every time you lite up. A professional welder told me that it also a no no to use a very dark lens. Something about you eyes having to stress to much cause of the darkness. But like stated above it would depend on what you are welding and how you are welding it.