I have been thinking about power density, brightness, etc and how it affect the brightness of beams and graphics for awhile. Bill Benner posted in another thread about the eyes response being around a log 5 function. That comment helped put some things in perspective... Is that %10 extra power really making that much difference in the brightness? This got me Sunday goggling. I found this site: http://www.telescope-optics.net/eye_...y_response.htm This is a great read. It gives a lot of insight on how we see projected images as we do. Pay particular attention the the section: Brightness vs. lightness. Happy reading.