My Mighty Bright works wonderfully on both powers, low and high. My only caution would be that one needs to carry around a lot of batteries if one reads for any extended period of time! This sucker really takes up juice. You don't notice it until the brightness begins to fade slowwwwwwly and one begins squinting to see. Plug it in and forget it. Works great at night so my wife doesn't wake when I decide to read at 2:00 a.m. (C'mon, I'm retired!) Buy it and enjoy bright light reading!