How far should plants be from the light?

[krustytheclown]

I have an air-cooled 400W HPS.

When starting seedlings, how close should I have them to the light? Currently they are 2 feet away.

As the seedlings grow into plants, how far should the plants be away from the light?

How about during flowering?

 

[Riboflavin]

2Ft is a good starting point. What are you temps like? If you can, keep inching them closer to 18 inches as they grow. Seedlings are fragile so you don't want to burn them with the light, but at the same time keeping them too far away can cause stretching.

 

[jammie]

hope this works

 

[facelift]

Great chart!

 

[d1ff1Ko1t]

I think u should be using cfl or fluoro lighting 4 ur seedlings instead of the HPS, its cheaper, uses less watts and its a better spectrum than the hps, its perfect 4 the stage when they dont need as much light anyways

 

[SaltyBalls]

yea 2 ft will work well

 

[etinarcadiaego]

Jammie: Where did you find that chart? Why is it called a "Lightning Chart" and what do those numbers in the columns represent? Actual lumen output at that distance?

 

[Riboflavin]

Right on, they are under fluro right now, a few more hours and they will be at 'day 7' since they broke the surface. I think I am going to start feeding soon at 1/4 strength and then move them back under the hps. Sound like a good idea?

 

[Mr. Hugeblunts]

Jammie: Where did you find that chart? Why is it called a "Lightning Chart" and what do those numbers in the columns represent? Actual lumen output at that distance?

There is a key at the top of the chart
Blue denotes inches from the lamp
yellow is denoting different wattages of light
the numbers are lumen output at that distance
green is good, grey is not good and red is BAD

 

[etinarcadiaego]

I'm just shocked to learn that my lamp is rated at 50,000 lumens whilst 6" from the bulb. Awesome news. +K to jammie for the Lightning Chart! Heh

 

[d1ff1Ko1t]

I think the feeding 1/4 strength nutes is a good idea, but i wouldnt rush putting them under Hps, unless they have at least 3 internodes.

 

[Herbalgardener]

I was wondering if I had 4 x 26watt daylight CFLs with a total of 6280 lumens, how far away can I keep the lights and still get optimal grow??

 

[smokincheeze]

I was wondering if I had 4 x 26watt daylight CFLs with a total of 6280 lumens, how far away can I keep the lights and still get optimal grow??

I have mine within an inch, I wouldn't go to far away...the ones close to the fan actually touch sometimes with no problems

 

[Herbalgardener]

thanx for the response smokincheeze. How many cfls are you using , how did it turn out?