50" ST60???

Do these settings apply to the 50" ST60 as well as the 55"? What ambient foot candle reading do you consider dimly lit to be? My room is 14'x16' covered with dark cedar boards walls and ceiling. The TV is centered on one of the 16' wallsThe 14' wall to the right of the TV has 3 large windows. Seating is along the opposite 16' wall. At it's brightest I get a reading of 40 foot candle in the room. Is this room too bright for a plasma TV