In a nutshell
Lumens per square foot:
Minimum amount of lighting needed is around 2000 lumens per square foot.
(Two 23 watt CFLs, per square foot*)
Mid range is around 5000 lumens per square foot.
(Three - 23 watt CFLs, per square foot*)
Optimal is 7000-7500, or higher, lumens per square...