Dynamo lights are one of those things you have to try to see for yourself just how good they are. On the spillover, though, because my dyno-driven lights illuminate the road, I find they don't affect my night vision. As a result, I can see things out of the corners of my eyes (like dogs, cats, turkeys, raccoons, and joggers in black) when riding with dyno lights better than I can with battery blowtorch lights. Don't know about deer, I haven't had any close encounters with deer at dusk or night so far.