how close lights/plants

hi ev'rybody ,im a firstime grower,i been reading on how to grow indoors four the past 2 months,i got a 400watt mh conversion lamp and a 400 hps,moisture max pottin mix for now,ff is on the way,got mg too but keep on readin its not good..the space im working with 2x3closet.i also got a metal trashbin which ill use to put a claypot inside.i need to kno how close cn i have my lights to the plant....

20 inches for a 400w HPS and use miracle grow organic mix

Is it enclosed ?

Its a good roule of thumb to put your hand where the plant would be and than mouve the light as close as possible without your hand feeling discomfort...Why would you keep your plant in the metal trash bin?

thanx for the advice guys..i do plan on puttin the plant inside the bin thinkin better or more reflection no?but if anyone think its best to get rid of the bin i shall then.

IMHO 20" is too far. I keep my 400 watt hps to within 7 - 8".

i have my 400w hps 6-10" from the tops of my plant at the mo, with a good fan blowing on them, and thay are doing fine, but i try for 7",,

Those charts, I don't understand them, they say that a 1000w hps has 140,000 lumens. At one foot away it should still be 140,000 lumens.

I don't get it at all. light = intensity divided by distance squared. So lumens should work out like this 1 foot x 1foot = 1 foot x 140,000 lumens = 140,000 lumens.

I'm lost.

so am i. but went ahead n got em at 7....thnx evryone for th e advice..

it's called the inverse square law. the farther away a light is from a plant, the less intense the light is at the level of the plant. this is true for all light sources, including the sun.

think of it this way, if the sun never lost its intensity the greater the distance between you and it, earth would be scorched and there would be no life at all. there would be no such thing as the night sky because all of the stars in the universe would be equally bright from any distance.

i do the same as that 1 guy.put hand on top of plant if the light dosnt burn your hand it wont burn the plant

i am no expert this is my first grow...check pics and let me no how im doing..thank you