400 watt light distance??

[yes_i_cannabis]

Hi guys, was wondering what the best distance to keep a 400 watt m/h light away from the tops of the plants is??
cheers

 

[4iiii'z]

close enough so it dont burn

(*)^(*)

 

[leroymmj]

As close as you can with-out burning them. 12 to 15 inches is close. Try the palm down method of testing with your hand. Your hand should not feel too hot.

 

[imnotcrazy]

My 400W HPS is air cooled and I can get it as close as 5-6 inches

 

[dre86]

with ventilator under it I'd say 1 feet is close

 

[aeric]

it depends on if it's directly under or to the side, and your reflector. even without aircooling (but with good ventilation) u can probably get them pretty close on the side (6") but directly under is more of a spotlight/heatlamp effect. your hands and eventually your plants will tell you before it's too late unless u like to leave alot.

 

[chepnut]

Light Chart

Light Chart

Give this chart a shot for the light amount, but then you are still going to have to use either your hand or a thermometer to tell if your canopy is getting to hot

 

[yes_i_cannabis]

exo..thanx to you all....heaps of good info...cheers

 

[sensirocker]

nice chart

 

[OceanGrowin]

yeah i got some yellowing right under the bulb..its a good foot away from the tops and the buds and leaves not directly under the bulb are lush green..could it be an old bulb or what??there og kush s1's, are they sensitve to light intensity?cause this should not be happing in my book..temps at 28 degree's and humditiy is unknown..only starting to form buds now so im worried that this will get even worse and ruin my hard work..cant get it any higher as my grow box was built a bit short(gonna make it bigger next grow)

 

[Guest]

radiant heat from hps is an easy way to kill the plants.Your branches will still be filled with potent buds if you take the lamp a bit further

 

[Maj.PotHead]

cheapnut that guide is for HPS
here's the 1 for MH

another good rule of thumb for proper lighting distance for MH/HPS is place your hand under the light as close as ya can w/out burning the hand. now back away untill your hand dosent feel hot hold it for a few min's to be sure. make sure your bulb is at operating temps when you run this test i use a cheap mecury fish tank thermostat at plants tops for my temps reading not the best but effective .

if your experincing lighter green growth at the very tip's the newest growth this dose happen usally when the leaves grow it they green up n/p.

ventilation is a key factor in a sucessful grow bringing in plenty of fresh cool air and expelling the hot stale air is a must. fans around the inside of grow for air circulation is a good helper. air cooled hoods or cool tubes are the best for heat control and allows for the closest placement of lighting.

remember the closer the lighting placement means the smaller the light foot print say a 400w MH @ 5 inch from plants tops has smaller print then say same light @ 12 inch's from tops

 

[Maj.PotHead]

yeah i got some yellowing right under the bulb..its a good foot away from the tops and the buds and leaves not directly under the bulb are lush green..could it be an old bulb or what??there og kush s1's, are they sensitve to light intensity?cause this should not be happing in my book..temps at 28 degree's and humditiy is unknown..only starting to form buds now so im worried that this will get even worse and ruin my hard work..cant get it any higher as my grow box was built a bit short(gonna make it bigger next grow)

.only starting to form buds now so im worried that this will get even worse and ruin my hard work..cant get it any higher as my grow box was built a bit short(gonna make it bigger next grow)

better modify your box now if your worried about height issues now just starting to flower they will stretch unsure about your ogkush s1's but a good rule of thumb for the stretch for 12/12
1st 2-3 weeks plants stretch major when flowering is induced a

sativa can stretch 3-5 times it's size when 12/12 was started during this time a
indica can 2-3 times it's size

your only hope is to modify your box now early into 12/12 also do a search on supercropping

 

[buzzed day]

you could scrog your plants to keep them short and mine is about 1 ft away but i'm going to empty my carboun scrubber-cooltube for a month or so to let it take out more heat and i should be abel to get it a littel closer peace

 

[OceanGrowin]

thanks guys..as ive got no money for wood to upgrade my box this week ive just tied them down..gave me some more room but still not enough..as long as i get a few buds im happy ..its an aircooled hood with good extraction and fresh air...everything fine cept for light distance i think..ah well canna nutes tend to give light green plants too ive heard,maybe thats the prob..as i look there not yellowing just pale green..should be right i think..

thanks again for the help guys