how far should mh be from my plants?

i built a flood and drain and was wondering how far my metal halise should be from my plants. the plants were just obtained from a medical dispensary so i dont know how old they are but they are about 5-8 inches and the light is 1000w and i have another that is 400w. how far should each of these lights be from the plants.

depends if it is air cooled, has glass shield, or is open. in general, 1000 needs to be kept 3 feet away, unless air cooled. 400 watt needs to be about 1 foot away unless air cooled.

No clue about the 1K, but my 400's seem to be OK at about 18". Any closer and I start causing discomfort and burning. I have a couple of 1K lights, but need bulbs for them

i used (im outside growing right now) a 400w mh, with a glass shield.. i kept it around 6inches from the tops without any problems... sometimes as close as 4inches; but that is pushing it...