Scrog screen distance to bulb?

[Power13]

All this discussion over distances... never could settle this in my head, so...

Does anyone have any scientific data regarding how much light mj can use? I get this is dependent upon a number of factors, e.g., temps, nutes, co2, rh, etc, but does anyone have any real data? I haven't ever seen anything...

The closest i've found dated back to '87 from Daniel Storm... has a chart in his book correlating light intensity & co2 levels to plant growth rates. No raw data, but the chart indicates that diminishing returns are reached at appx 6500 lumens x 1300 ppms co2... anything over & above has very little impact to maximum growth rates.

With this in mind, what exactly would the benefits be of placing the plant tops so very close to the light such that 40k lumens is achieved??? Is it really doing anything of benefit, or perhaps even slowing "ideal" growth rates?

The benefit I've always noticed was plant canopy density & overall footprint maximization. These two components to verti output is dependent on casting a wider arc of light... 360d in fact. So, if you had stacked 1000's, or even a single, you will get more footprint by having the bulb 2' feet away vs 12". The 2' will have more plant canopy available & will still over saturate the canopy w max usable lumens.

Is this way off base?!? Peace.

Bob,

Thanks for posting this. I've been thinking this over in a lot of ways. The only way to figure this puzzle out, will be for me to buy a light meter, and figure out the distances from the cool tube, and see how many lumens i get. I've read in many places that 5k lumens is about where you want to be for each bud, thus your 6500 lumens doesn't seem far off.

There is a thread on icmag about testing different reflectors, i'm going to take a look at it and see where their average is. That will give us a rough estimate. However, since we don't have a reflector and are vertical, i think it will be less. Thus the need for my own test.

 

[squirrelfooker]

4ftx3ft room. I run a 600 watt inside a cooltube with the screen 5 to 6" from the glass, so about 7 to 8" from the bulb. They do fine and can almost touch the tube before starting to bleach/burn. The problem is the small diameter screen means the plants touching it block light to the rest of the plant. I will make it bigger next time to let the light penetrate better. Probably 10" from glass to screen instead of 6".

 

[pong]

From experience
250 - 12" diameter
400 - 14"
600 - 16"
That's the diameter of the lamp 'scorch screen' inside that they scorch, pull them off a bit and all is OK

Been doing this for years

Bush

what distance do you suppose the scorch screen should be at for a 1000w hps?

 

[Power13]

what distance do you suppose the scorch screen should be at for a 1000w hps?

Pong, I would use a screen a 24" screen. You can get closer if using a cool tube though.

 

[RipVanWeed]

I use a vertical ScroG and let my buds get about 8"-10" to the 1000w. They bleach and start to crisp up if they get too much closer. Get as close to your light as heat will allow, put a fan on the floor pointing up so it blows straight up at the light bulb. The distance from the light source has a tremendous affect on the size, density, and potency of the buds.

Here let me show how mine's setup

 

[mrred]

im going try a 20" diameter chicken wire under a 150
150 has 12 inches of viable light and it 2 sides so thats 24 inches of good light, i plan to get the screen filled up, then let it grow past the screen 1 or 2 inches then flower

 

[LacyLePlante]

what was the outcome?

what was the outcome?

I personally use air cooled hoods so i can get my buds right under my 1000's. i shoot for about 10-12 inches from my canopy (scrog) , i only raise if heat is an issue!

 

[asshole]

250 - 12" diameter

I disagree.
250 watts hps can be much close than 12 inches.
6 or 7 inches will not burn them, maybe closer depending on ventilation.

 

[ibjamming]

Have you looked into 400 watt CMH bulbs? I can't stress enough how great these bulbs can be. Many growers really overlook its advantage. Besides the better spectrum, same lumun output as an HPS, and less heat, its real advantage is how close you can bring your plants to it.

I just got one yesterday... It sure is a WHITE light...and very bright. I sure hope the girls like it...

 

[hilbie]

I use a vertical ScroG and let my buds get about 8"-10" to the 1000w. They bleach and start to crisp up if they get too much closer. Get as close to your light as heat will allow, put a fan on the floor pointing up so it blows straight up at the light bulb. The distance from the light source has a tremendous affect on the size, density, and potency of the buds.

Here let me show how mine's setup

theres no link to potency at all, and also i would like to remind people that heat stress ruins yeild, dont get to overzealous about a few inches if u now its just too hot to be under or next to for two plus months without a passing cloud or rain storm for relief. seen plenty of ''running buds'' too close to 1000 bulbs that lost weight due to heat stress. alot of your plants would actually grow better if u back them up a few inches imo.

 

[Romple-Stomple]

I've read in many places that 5k lumens is about where you want to be for each bud, thus your 6500 lumens doesn't seem far off.

Hi guys, I think you might be confused about your units of measurement. A light meter doesn't measure lumens, and Power, the "5k" is referring to foot candles. Ed Rosenthal references this stat in his "Marijuana Grower's Handbook."