rule of thumb
Lumen depends actually on the type of light u use ...
For HPS natriumlamp use the following as a guide
250 Watt -> 31000 Lumen, good for 0,5 m2
400 Watt -> 55000 Lumen,good for 0,7 m2
600 Watt -> 98000 Lumen, good for 1,2 m2
Alsways watch out for the distance to...