Light Spacing Questions

GorrillaPanic SNP said:

Do you think lower yields in association with closer lights could be related to heat-stress, burning, or any other heat related issues...or purely a light spread issue?

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Generally speaking, all things being equal, much of it is due to poor dispersion. IME, a plant can be conditioned to sit very close to, say, a 1000HPS. It's definitely doable. Ask me how I know. This act, however, doesn't keep the plant terribly healthy for its entire life. The last couple of weeks seem to show the most sensitivity. Intuitively, I attribute it to too much light intensity. Heat isn't really an issue in my setup.

It is brutally obvious. I'm basically asking a loaded question, which i know the answer to, but asking it none the less to make sure someone doesnt pop up and say "so and so hood brand blocks heat better"...

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Fair enough.

Lets say you had a glass panel that kept most, if not ALL, of the heat radiated from the bulb from passing through to the plants while still allowing the full spectrum of the bulb to reach the plants...do you think you could improve quality and yields by moving the light a few inches closer that normal?

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Ultimately, yes. This being said, shot term, glass will absorb and (kinda) equalize the heat within the space between it and the lamp. I imagine there's a glass compound that reacts to such a thing better than others, perhaps extending the time before the glass reaches a relatively high temperature. So, long term, meaning a typical 12 hour cycle, I have very serious doubts.

Simon

I use an air cooled hood using a 600. My area is 4x4 I usually run 6 plants. I have tried keeping my plants around 7in from the light. Results were average. Moving it to 12in greatly increased my yield. My lower buds were much denser and danker. Top colas remained the same size either way. To each his own.

Getting better lowers moving light away. Strange phenom imagine the buds with no light.

SimonD said:

Generally speaking, all things being equal, much of it is due to poor dispersion. IME, a plant can be conditioned to sit very close to, say, a 1000HPS. It's definitely doable. Ask me how I know. This act, however, doesn't keep the plant terribly healthy for its entire life. The last couple of weeks seem to show the most sensitivity. Intuitively, I attribute it to too much light intensity. Heat isn't really an issue in my setup.

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Yes a plant can be "conditioned" to sit closer to a hot 1000w hps, and I would assume it would not be too great for the plant, but what i am talking about is not "conditioning" in anyway...I'm talking about being able to put your light closer to the plant with NO heat and NO stress...the plant would essentially have the same health as a plant with the light 12"-18" away, but the light would be more like 5"-7" away (or closer/farther depending on light spread etc). With the light closer, without the heat or stress that usually comes with moving a light closer, the intensity would be greater resulting in tighter nodes. In Ed Rosenthal's Marijuana Grower's Handbook, he says "During the growth cycle, most varieties will do well with 2000-2500fc, (21,500-27,000 lux,...) although the plants can efficiently use 5000fc (54,000 lux,...) or more. The more light they receive during vegetative growth, the faster their growth and the sturdier their stems." So I don't think intensity was the problem...

SimonD said:

Ultimately, yes. This being said, shot term, glass will absorb and (kinda) equalize the heat within the space between it and the lamp. I imagine there's a glass compound that reacts to such a thing better than others, perhaps extending the time before the glass reaches a relatively high temperature. So, long term, meaning a typical 12 hour cycle, I have very serious doubts.

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I agree glass does tend to "equalize" to ambient temp, and over a 12-hour (or even 24 for veg) cycle, the glass would heat up and thus transfer that heat towards the plants...but if you had a specially designed coated glass that reflects most, if not all, heat and keeps it from reaching the plants...this would eliminate the root problem with moving your lights closer, allow you to move them closer (to a position of your liking) and improve your plant health, growth, quality, and yield...

herbbilly said:

Getting better lowers moving light away. Strange phenom imagine the buds with no light.

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What?

If raising light 12" from lower buds increases yield. Imagine yield if there wasn't any light. What a positive attribute.

My space is crowded. By raising my light it helped with overall coverage of plants.

zack66 said:

I use an air cooled hood using a 600. My area is 4x4 I usually run 6 plants. I have tried keeping my plants around 7in from the light. Results were average. Moving it to 12in greatly increased my yield. My lower buds were much denser and danker. Top colas remained the same size either way. To each his own.

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zack66 said:

My space is crowded. By raising my light it helped with overall coverage of plants.

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Ya 6 plants in a 4x4 is pretty tight...

GorrillaPanic SNP said:

Ya 6 plants in a 4x4 is pretty tight...

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How do you know? Seriously, how do you know? What experience do you have that leads you to such a conclusion in a vacuum?

Do you have some plants you can post, so that we can see who we're talking to?

FWIW, I'd run 12-16 in that space trained and pruned for no-popcorn. Ed's book didn't teach you how to maximize yield? Make sure you cure before you dry, as Ed suggests, as well.

GorrillaPanic SNP said:

Yes a plant can be "conditioned" to sit closer to a hot 1000w hps, and I would assume it would not be too great for the plant, but what i am talking about is not "conditioning" in anyway...I'm talking about being able to put your light closer to the plant with NO heat and NO stress...the plant would essentially have the same health as a plant with the light 12"-18" away, but the light would be more like 5"-7" away (or closer/farther depending on light spread etc). With the light closer, without the heat or stress that usually comes with moving a light closer, the intensity would be greater resulting in tighter nodes. In Ed Rosenthal's Marijuana Grower's Handbook, he says "During the growth cycle, most varieties will do well with 2000-2500fc, (21,500-27,000 lux,...) although the plants can efficiently use 5000fc (54,000 lux,...) or more. The more light they receive during vegetative growth, the faster their growth and the sturdier their stems." So I don't think intensity was the problem...

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As Ed has all the answers, why waste my time? .

I agree glass does tend to "equalize" to ambient temp, and over a 12-hour (or even 24 for veg) cycle, the glass would heat up and thus transfer that heat towards the plants...but if you had a specially designed coated glass that reflects most, if not all, heat and keeps it from reaching the plants...this would eliminate the root problem with moving your lights closer, allow you to move them closer (to a position of your liking) and improve your plant health, growth, quality, and yield...

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I'm done with this.



Simon

GorrillaPanic SNP said:

Thanks for the info KK. When you say "Hoods trap heat above the canopy vented or not", is that because the glass panel lets heat pass through? So if you had a glass panel that reflected heat, while letting the whole spectrum pass through, you could move the light closer to the plants and improve intensity and penetration?

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No, the reason is because of the hood itself. Heat rises and since the hood prevents that, the heat can ONLY be radiated downward to "escape" the hood (which is why vented hoods exist) but they are still designed to reflect light AND heat downwards.
if you want to avoid this and get your lights closer, try vertical lighting. I got 3 400w hps and 1 400cmh bulb strapped together with zip ties hanging vertically in the center of a 4x4 tent. Tents hit 90 (but I got co2) plants love it vertical is much easier to cool with much less ducting. All you really need is a fan to help push the already rising heat up. The radiated heat off the bulb isn't aimed down anymore, it's spread all around evenly and thus is "cooler" and plants can be closer. I keep mine a good 12" away but cud put them 6-8" if I wanted. But no reason for that much light lol.

PS I had 2 dual bulb hoods (growzillas) in the tent before (800w total ea for 1600w) and my temps exceeded 105. Damn hoods just would not cool fast enough, I could easily have cooked eggs on my hoods.

Hope that explains
Sir KK