How close should my plants be to the bulb?

I use a r1000 Multi-Vapor 1000 watt bulb as a light for my plants. I wanted to know how close in feet should my plants be to the bulb?

A bare bulb with no cooling system , I would do at least 18 inches to 2 ft away.
But still do the back of the hand test , if its Too Hot for your hand its Too Hot for the ladies..
Good Luck...

Along with what cocakola said.
I put the back of my hand directly under the light till it's uncomfortably hot, then I lower my hand until it's no longer hot....that's the closest I put the light to the top of the canopy.

Good luck.

Thanks a lot guys for the input guys, my lights now hanging from the ceiling in my grow room. My plants have been doing just fine like that except I overwatered them a little. I can post some pictures in a bit if anyone wants to check it out. Peace