how close can i put cfl's ?

I got 4 100w 6500K cfl's how close can I put them to my plants I don't want to burn them ? In my avatar picture you can't even see bulbs how close is to close ?

Keep them about 2-3 inches at the least, any closer will most likely burn your leaves.

another rule of thumb is.... put your hand on the top of the plant. then move the bulb down until you feel heat from the bulb. move the bulb slowly away until you dont feel the heat anymore. which is about 2-3 inches when using a cfl

I get them as close as possible. CFL's lose lumens quickly so I figure the closer the better. I've paid with a few burnt leaves, but only if they actually touch the light. I've never really seen any negative consequences as long as it doesn't happen all the time. Doing this you have to move the lights multiple times a day during veg and especially during your big flowering stretch.