What distance should my light be from my plants?

according to the chart, a 400w light 18" from the plants would produce 7074 lumens, 4 inches lower the light is producing 4735 which is below the threshold for what they consider acceptable

this means the top 3 or 4 inches would get just enough while the lower stuff would really struggle to thrive...

also for reference I think the minimum lumens needed for growth are about 2000, mind you this is exluding LED's...
 
hey 420 magazine world!

i am totally new to this stuff. i just got my first clone about a week ago. it started off healthy and is turning yellow at the tips and around the edges of the leaves.

i.d.k. if it is a light problem with it being too close (using a florescent light that is equivalent to 100 watts) its about 5-6 inches above the plant or if it is a nutrition problem.

any kind of help would be appreciated. if it helps to add some pics, i shall do so
 
Keep in mind that you should use some type of reflective material, such as mylar, in your grow space so the that the light doesn't just affect the tops of the plants.
 
i just put my clones that are about 1 ft tall, under my 1000w hps at about 2 ft for a couple of hours and they started wilting. so i doubled the height, what do u guys say?
 
pez4life said:
i just put my clones that are about 1 ft tall, under my 1000w hps at about 2 ft for a couple of hours and they started wilting. so i doubled the height, what do u guys say?
Click to expand...

what are your temps? do you have active air cooling on light?

If you had them under something like flouro's then you need to raise your light to top position and gradually lower from top position to lowest position in a week or so...

I had the glass of the hood for my 1000HPS as close as 6" from tops of plants without any heat damage. Its active air cooled and I didnt keep it that close for too long but mature plants should be able to withstand 24" from 1000HPS
 
pakalolo408 said:
hey 420 magazine world!

i am totally new to this stuff. i just got my first clone about a week ago. it started off healthy and is turning yellow at the tips and around the edges of the leaves.

i.d.k. if it is a light problem with it being too close (using a florescent light that is equivalent to 100 watts) its about 5-6 inches above the plant or if it is a nutrition problem.

any kind of help would be appreciated. if it helps to add some pics, i shall do so
Click to expand...

5-6 inches from a 23w cfl is prob not enough light to keep plant alive... you need that bulb much closer, you could have the bulb pretty much touching the plant and it would barely be getting enough light...

but you might have nut problem as well or be over water/ph too hi/low... why dont you start a new thread with pictures of your plant and people can help diagnose...
 
bizz said:
5-6 inches from a 23w cfl is prob not enough light to keep plant alive... you need that bulb much closer, you could have the bulb pretty much touching the plant and it would barely be getting enough light...

but you might have nut problem as well or be over water/ph too hi/low... why dont you start a new thread with pictures of your plant and people can help diagnose...
Click to expand...

thanks man i'll get started with a new thread with photos in a few days (need time to prep stuff for my first child, expecting him to pop out soon)

for now i moved the light really really close, its literally right on top of the plant. if anything, i will change the lighting system. this is my first grow ever and i hope it comes out great, but it is going thru tons of stress with the over water, trimming, and i dont even know. everything is turning yellow and i might just throw it away and start a new one, but we'll see1
 
Hey smokey, what's this you say about the position of the reflector? you mean if I have a 2x4 space, the 18x36 reflector should be hanging with the 18" side parallel to the 4' side? let us know!

Thanks
 
anthonyps33 said:
Hey smokey, what's this you say about the position of the reflector? you mean if I have a 2x4 space, the 18x36 reflector should be hanging with the 18" side parallel to the 4' side? let us know!

Thanks
Click to expand...

its not so much reflector as it is bulb, think about it

the filament goes from top of bulb to bottom, so the bulb doesnt put out much light above its top or below its bottom compared to how the sides get lots of light
 
bizz said:
You might find this chart useful

1157989-Foot-Candle2520Chart2520HPS.jpg
Click to expand...




This chart really doesnt make sense. I have a digital light meter and my 600w sits about 13 inches above my tops and reads 5500 to 2800 lumes in the corners. I know over 10K lumes with HID can cause bleaching but as the chart shows capable of going much higher than that. Have you guys measured your lumes in your garden? My bulb is on its second grow but maybe its weak shown in the readings. Good Thread
 
A good general rule for "how close" is you place your hand between the light and the plant, palm down. The sensitive skin on the top of your hand has about the same sensitivity as the plant, if your skin is uncomfortable, so will the plant be. If the skin is fine, same for the plant. This addresses temperature only, not footprint
 
well in that case i can drop my light a few inches too then. i am only growin 1 plant with a 250w hps about 18" above the plant and the temp sit at 22C when lights on, gonna lower it to 12" and see how she gets on

thanks guys
 
jambo stoner said:
well in that case i can drop my light a few inches too then. i am only growin 1 plant with a 250w hps about 18" above the plant and the temp sit at 22C when lights on, gonna lower it to 12" and see how she gets on

thanks guys
Click to expand...

Hey my friend anytime you're dealing with a HID light it's a good practice to only move it 1-2" at a time. 6" is a lot at once. Drop it 2 inches, give them a day, see how they're doing, and repeat. Good luck!
 
littlelil said:
:thankyou:I thought marijuana was supposed to destroy brain cells, after reading this, I doubt that it is true.:smokin:
Click to expand...

no not destroy them more or less can help develope some thats why they use it in brain disorderd disseses like huntensones parkinsons spasticism etc: it helps also with the brains functions that control spasms in the muscles something along those lines anyways so keep toking,, have a look through stuff like this if you dsont use it now then you will ;) peace: Cannabis - Wikipedia
 
Barry Manilow said:
Hey my friend anytime you're dealing with a HID light it's a good practice to only move it 1-2" at a time. 6" is a lot at once. Drop it 2 inches, give them a day, see how they're doing, and repeat. Good luck!
Click to expand...

hi there, if i have a small office fan to blow under my light but obviously at a small distance away from the light relflector, does this mean that i can put the light even closer,, its a philips master son-t pia plus 400 watt, i have it at 12" at the moment, without the fan blowing.. cheers;)
 
Back
Top Bottom