how close should the lamps be?

[Christophe]

1m? 50cm ? plz help 400watt :o

[GTC21]

see this thread...

http://boards.cannabis.com/showthread.php?t=13788

[Zandor]

There are two factors to consider. Temperature is first; monitor the temperature at the average height of your plants. To close and you burn the tips to far away and you give up luminance penetration (PAR). Second is Luminance loss. Most experts are in agreement that light intensity diminishes exponentially fast.
For example:
A 400-watt MH from 0â?� to 12â?� is about the same luminance say 55000
Same light at 24â?� the luminance is now about 30000

Still good

Same light at 36â?� the luminance is now about 12000
Fan leafs block most of the light so nothing below sees enough of the light of day to do any good.

For me about 16â?� is average if my plants get too tall I just bend them over (if you bend them over the buds get more light and grow bigger)

I hope this helps

Peace

[del...]

hold the back of your hand under the hot light. find the spot where your hand begins to feel uncomfortable, add a bit for growth and hang...watch closely and adjust as needed. sometimes you'll have to raise it every other day but it's worth spending the time keeping your light at the most efficient level...especially during flowering. but be careful not to burn...burned parts will not recover.