auto flowerin lighting question

ive got a variety of lowriders going in a small space, and am using a 400w mh light for veg,, it is dimmable,, would it be more efficennt to dim it down to 50% if there only about 2 inches tall? to save energy? when should I run it at 100% power? thanks

I let my autos go for about 2-3 day's in normal sun light then switch my 600w hps on and everything is good to me, mh is a bit different to hps tho

either way
i start mine under the same light i finish them under

i was just wondering if running my light full powers is wasting light/electricity when there just 2 inches tall or so.

I would turn it down and save on electricity and less heat.

I jus use cfl for 2 weeks then off to mh...if u fell like you are wasting light jus puth them on a box..but it doesn't bother me if they are far away from the light bcuz eventually they will grow and flower n stretch as well