[Sanddancer]

The psychology of light is much more complicated than just number of lumens being thrown about. Because HPS lamps throw light in pretty narrowly defined bands, people feel less comfortable, and aren't able to notice things as well compared to light that is lower wattage, but more full spectrum ( http://www.lrc.rpi.edu/researchAreas/pdf/GrotonFinalReport.p... ). Like a lot of things, quality of light counts more than quantity.