optimal distance of 400 hps

indyman said:

hey bro it all takes place in the hoodmine is at 10in and no prob.i'm not even cooling the light it has 8" hole on each side.Light works like this it is mearsured at 12" from canopy 50,000 lumens and the farther away it gos it loses lumens by half like 18" 25,000 lumens at top of canopy.Now if ur plant is 3 feet tall the light is 4ft from base of plant if my math is right about 12,500 lumens.so the closer u get the light the better off u are.If i cooled my light could get it about 6in away and that means now the lumens are 100,000 lumens at the top of my canopy and thats basicly how light works.good luck bro!!HOPE THIS HELPS!

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This guy has the right idea about how lumens work!

What he is saying is that every 6 inches further from the light you get, you lose half the lumens (or for every foot you move away the lumes drop to a quarter of the strength...

So a 1000w light that puts out...
160,000 Lumens at 1 foot
40,000 Lumens at 2 feet
10,000 Lumens at 3 feet
... (after this point you won't get optimal growth.)

Therefore, the higher the wattage/lumens, the better your canopy penetration will be and the taller plants you can grow.

Edit: Fucked up my math.

mismos00 said:

No, I read in Jorges Cervantes Marijuana Bible that 10,000 lumens is the MINIMUM for optimal growth in the flowering stage (maybe you're thinking about the vegetative stage?)

Did you know a 1000w puts out over 160,000 lumens.

I don't mean to get into a thing about this... just google it... you're a little off. I've been reading about this for a couple of days.

Maybe you're thinking of lumens per square foot?

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10,000 lumens per square foot maybe if it's a MH light in flowering. With HPS 10,000 lumens per square foot is much greater than the minimum!!! The square foot is how it's measured, not total lumens. 3000-5000 lumens per square foot of HPS is enough for satisfactory growth. The main benefit of the higher wattage would be the fullness of the buds at the middle and bottom of the plants from the extra penetration power.

Also, don't forget that if the top is too close to the light it may continue to stretch for a longer period of time substantially increasing your time until harvest,especially if the sides are closed in (aka squished plants). I'd keep it 10-12 inches away, just like the rest said. Easiest way to avoid frying bud/leaves, heat stress, late stretching, and bleaching.

mismos00 said:

This guy has the right idea about how lumens work!

What he is saying is that every 6 inches further from the light you get, you lose half the lumens (or for every foot you move away the lumes drop to a quarter of the strength...

So a 1000w light that puts out...
160,000 Lumens at 1 foot
40,000 Lumens at 2 feet
10,000 Lumens at 3 feet
... (after this point you won't get optimal growth.)

Therefore, the higher the wattage/lumens, the better your canopy penetration will be and the taller plants you can grow.

Edit: Fucked up my math.

Click to expand...

Very good way of putting it in relation to height, wish I had read your msg before posting.

clift709 said:

10,000 lumens per square foot maybe if it's a MH light in flowering. With HPS 10,000 lumens per square foot is much greater than the minimum!!! The square foot is how it's measured, not total lumens. 3000-5000 lumens per square foot of HPS is enough for satisfactory growth. The main benefit of the higher wattage would be the fullness of the buds at the middle and bottom of the plants from the extra penetration power.

Also, don't forget that if the top is too close to the light it may continue to stretch for a longer period of time substantially increasing your time until harvest,especially if the sides are closed in (aka squished plants). I'd keep it 10-12 inches away, just like the rest said. Easiest way to avoid frying bud/leaves, heat stress, late stretching, and bleaching.

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I wasn't talking about lumens per foot.

Well what does 5000 lumens per foot even mean? At what distance should you be getting this 5000 lumens per foot? I'm sure you do realize the lumens drop the further away you move from the light. I don't care about the lumens hitting the ground, I want to know how many lumens are hitting the canopy.

clift709 said:

Very good way of putting it in relation to height, wish I had read your msg before posting.

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I'm glad you saw my second post... could you still elaborate on the lumens per square foot thing... I don't understand how that's suppose to work.

lumens per square foot means how much light is hitting each square foot on the surface of the canopy of your plants which is different than how many lumens you get from moving the light further away from the canopy at a single point from the light to the top of a plant. just to clarify lumens comes from "foot candles" which is how much light diminishes from a single candle at each foot moving away

as for how far you should put the light. well it depends on a lot of things. how old are your plants? how tall are they? are they sick? i've experimented and i've found that with clones you shouldn't keep the light at maximum distance because they are using their energy to grow new roots rather than collect light and protect its waxy coating. so usually 24" -34" is enough light for 8 8inch pots.

now as they grow and get stronger and start to grow a lot of healthy leaves for collecting light and they have a nice dark green color (for most strains) you can move the light closer to the plant as long as you have proper airflow and humidity. i've also found that will clones, if you blow them too much with fans you will dry them out. especially if the light is low and the surface of the canopy is real hot. the tips of the leaves will start to curl them brown and the sides of the leaves will roll up to try to shade itself from the intense light and the heat/low humidity.

its all about reading your plants. they will tell you what wrong will them. slowly adjust different aspects to try to narrow down optimum conditions for the grow area.

i imagine in am optimum climate with perfect temp/humidity/water and airflow (wait did i just describe mother earth?) you can have the light around 10"-18" it also takes a real good light to acheive this. lower end lights get too hot and should be moved further to reduce heat. also raising the plants instead of lowering the light promotes airflow. try not to point fans directly at plants until they are strong enough or around a foot tall

mismos00 said:

No, I read in Jorges Cervantes Marijuana Bible that 10,000 lumens is the MINIMUM for optimal growth in the flowering stage (maybe you're thinking about the vegetative stage?)

Did you know a 1000w puts out over 160,000 lumens?

I don't mean to get into a thing about this... just google it... you're a little off. I've been reading about this for a couple of days.

Maybe you're thinking of lumens per square foot?

Click to expand...

you been doin a lot of reading huh.... ive done a lot of growing 5-7000 lumens per sq ft. minimum of 3 if you really dnt care...... somone mentioned canopy penatration.... learn to grow with a horizantal light and penatration wont be as important you dnt grow tall plants you want to train them so you have an even canopy and all tops are the same distance from the light source dnt worry so much about light and learn to train plants to grow how you want not how they want. lumens are mesured at 1 foot from the light source which is right around where your canapy should be anyway..........oh and yes i do know how much light a 1000w puts out........ do you not know that lights are mesured in lumens per sq ft. and to have over 10,000 lumens in a room means nothing. could be too big could be too small depends on the room size

tusseltussel said:

you been doin a lot of reading huh.... ive done a lot of growing 5-7000 lumens per sq ft. minimum of 3 if you really dnt care...... somone mentioned canopy penatration.... learn to grow with a horizantal light and penatration wont be as important you dnt grow tall plants you want to train them so you have an even canopy and all tops are the same distance from the light source dnt worry so much about light and learn to train plants to grow how you want not how they want. lumens are mesured at 1 foot from the light source which is right around where your canapy should be anyway..........oh and yes i do know how much light a 1000w puts out........ do you not know that lights are mesured in lumens per sq ft. and to have over 10,000 lumens in a room means nothing. could be too big could be too small depends on the room size

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So you were thinking in lumens per square foot! Simple misunderstanding.

The box my bulb came in and my Jorges Cervantes Marijuana Bible talks about total lumens. Understanding how many lumens are produced at different distances from the bulb allows me to position my plants and helps me know how tall I can grow my plants.

I haven't run into the 'lumes per square foot' thing and I am still not sure if I understand it. I guess it makes more sense if you are growing SOG or something?

mismos00 said:

So you were thinking in lumens per square foot! Simple misunderstanding.

The box my bulb came in and my Jorges Cervantes Marijuana Bible talks about total lumens. Understanding how many lumens are produced at different distances from the bulb allows me to position my plants and helps me know how tall I can grow my plants.

I haven't run into the 'lumes per square foot' thing and I am still not sure if I understand it. I guess it makes more sense if you are growing SOG or something?

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sure, ummmmmmm lum per sq ft shows how big a room you can use a light in efficiantly find how many sq ft you can have maintaining 5-7000 per sq ft and pack that space full of weed . so if your 400w hps puts out a total of 50,000 than you take that 50, and put it in a 3x3 room thats 9 sq ft. so 50,000/9=5,555 lumens per sq ft 1 foot from your hood and thats where you want your canopy top fim lst whatever it takes to get all your tops at that hight thats what you need to do. tall plants dnt do so well indoors you wanna keep em under 3- ft. with an evan canopy .unless you go with horizantal lighting a 400w wont have the penatration so use light wisely keep it a foot away and top or lst so multiple tops are growing at the same hight and get the same light intensity. 10,000 total lumens would ony be enuf for like a 1x2 room you need to take advice and not think about growing tall plants you would get more weight, tighter buds and better smoke if you grew short bushy plants than tall ones, flower at a keep. dnt go around quoten books like they are all knowing they arnt they are just there to give an idea to get you started, the real growing begins when you throw that book away

tusseltussel said:

sure, ummmmmmm lum per sq ft shows how big a room you can use a light in efficiantly find how many sq ft you can have maintaining 5-7000 per sq ft and pack that space full of weed . so if your 400w hps puts out a total of 50,000 than you take that 50, and put it in a 3x3 room thats 9 sq ft. so 50,000/9=5,555 lumens per sq ft 1 foot from your hood and thats where you want your canopy top fim lst whatever it takes to get all your tops at that hight thats what you need to do. tall plants dnt do so well indoors you wanna keep em under 3- ft. with an evan canopy .unless you go with horizantal lighting a 400w wont have the penatration so use light wisely keep it a foot away and top or lst so multiple tops are growing at the same hight and get the same light intensity. 10,000 total lumens would ony be enuf for like a 1x2 room you need to take advice and not think about growing tall plants you would get more weight, tighter buds and better smoke if you grew short bushy plants than tall ones, flower at a keep. dnt go around quoten books like they are all knowing they arnt they are just there to give an idea to get you started, the real growing begins when you throw that book away

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So I have a 430w and a 600w, producing around 150,000 lumens. My canopy is roughtly 4x6 feet (=24 feet), so divide 150,000 / 24 = 6,250.

Is this correct?

So by this calculation I'm just in the optimum range at one foot away... so at two feet away I wouldn't be able to grow optimally?

By the calculations in Jorges Cervantes grow book (sorry to refer back to my bible), and from my own (albeit limited) experience with the lights I have, and from looking at other peoples grows, I am pretty certain you can grow big healthy plants at least 4 feet tall with a 600w (I have, like you mentioned, tried to keep my plants under 3 feet).

So between the above calculation (assuming I did it correctly) and the calculation/chart I and somebody else here produced (based on distance from the bulb) these numbers are telling us very different things.

Your calculations seem to suggest I have optimal lighting at just one foot away... my and Cervantes calculation suggests I have optimal lighting for up to three feet away.

So, I guess I'm still confused. I'll do some of my own digging, but do you have any references or links that spell out what you're talking about.

Another reference for light coverage...

https://www.rollitup.org/view.php?pg=faq&cmd=article&id=59

Things to know about lighting...
https://www.rollitup.org/view.php?pg=faq&cmd=article&id=259

"The minimum amount of light required by marijuana plants is around 3000 lumens per square foot. However, it's not 100% accurate, since although you may have a 10,000 lumen light, the amount of light that reaches the plant varies with the distance between the light and plants, and reflectivity of the grow box. The ideal amount is somewhere around 7000-10,000 lumens/sqft, and as long as the plants do not burn, as much light can be used as you want.
(*note, the sun produces about 10,000 lumens/sqft, on a sunny summer day)."


So it sounds like you'll want to take into account distance at some point, especially if you're not just growing 1 foot tall plants.

(on a side note, damn the search functionality on this site is poor!)

mismos00 said:

So I have a 430w and a 600w, producing around 150,000 lumens. My canopy is roughtly 4x6 feet (=24 feet), so divide 150,000 / 24 = 6,250.

Is this correct?

So by this calculation I'm slightly under the optimum at one foot away... so at two feet away I wouldn't be able to grow optimally?

By the calculations in Jorges Cervantes grow book (sorry to refer back to my bible), and from my own (albeit limited) experience with the lights I have, and from looking at other peoples grows, I am pretty certain you can grow big healthy plants at least 4 feet tall with a 600w (I have, like you mentioned, tried to keep my plants under 3 feet).

So between the above calculation (assuming I did it correctly) and the calculation/chart I and somebody else here produced (based on distance from the bulb) these numbers are telling us very different things.

Your calculations seem to suggest I have barely optimal lighting at one foot away... my and Cervantes calculation suggests I have optimal lighting for up to three feet away.

So, I guess I'm still confused. I'll do some of my own digging, but do you have any references or links that spell out what you're talking about.

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you do have optimal lighting. 3000 minimum so if you have 6250 than 3 feet away your prolly around that minimum... you can grow big healthy plants 4 ft tall but the bottom third of the plant will get a lot less light and wont really be good for anything but hash, wich is fine if thats what you want but your not goona fit but 2 or 3 plants in that space having them that big. i may have just come on your thread and confused you more than needed and for that i appologize... so if you grow i tall plant with a big cola or 2 and a bunch of useless crap or a 6 smaller toped or lst plants and get a shit ton o bud rather than long stems with little nugs on em your light will only penatrate so far and then your beat. ive had 6 big 3 ft plants not produce as much as 2 1 footers for that simple reason. hight does not = more bud. if you keed toping that plant and tying it down a bit so lower nodes have a chance to grow up and keep the canopy nice and evan you will end with several nice thick cola's and not much lower growth that wouldn't have gotten enuff light anywayits all about useing your light correctly i will post a few links that may be helpful

https://www.rollitup.org/general-marijuana-growing/723-things-know-about-lighting.html
lot of bullshit here but may help a little


https://www.rollitup.org/subcools-old-school-organics/106938-canopy-managment-101-a.html great info here

i kept my 400 watt light as closeas i could last grow and this grow ive been around 12-18" to get more of a spread. plants are doing much better this time around

stringd2002 said:

If you've only grown under CFL's you are going to be blown away by the difference in every aspect of the grow with a 400 watt system. It would make a huge difference if you could veg under 400 watt MH then go to 400 watt HPS for flowering. Have you already purchased a HID setup yet?

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Yea i ordered both bulbs. I got this awesome kit from HTGsupply. Its called the
400 Watt Organic Soil Grow Kit

You can click the link to check it out. Im so excited to get it started should come in the next week. Then Ill start updating my journal in my sig.

^A little word of advice.....stick with the HPS bulb throughout the grow, and you'll have better results. I compared those exact two bulbs against each other, and the 55,000 lumens of the HPS outperformed the 28,000 of the MH conversion bulb, even though the MH has a better spectrum for growing. Also, the MH lost intensity really fast, and after 3 weeks or so, i bet it had dropped down close to 20,000 lumens.

IMO, the 400 watt MHs are a waste of energy, and money.

jawbrodt said:

^A little word of advice.....stick with the HPS bulb throughout the grow, and you'll have better results. I compared those exact two bulbs against each other, and the 55,000 lumens of the HPS outperformed the 28,000 of the MH conversion bulb, even though the MH has a better spectrum for growing. Also, the MH lost intensity really fast, and after 3 weeks or so, i bet it had dropped down close to 20,000 lumens.

IMO, the 400 watt MHs are a waste of energy, and money.

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mh lighting the first 2 weeks of flower will help minimize streatching at least thats what ive found

I've kept mine as close as 6-8" without problems; always have a fan blowing over the tops, but no real "ventilation system". But, this time around I've been trying to stay about 12-16 inches up to get a better spread over all of the plants and their parts.

And, I have light-bleached some plants with my 400, although it's not easy to do.

Knowing how your strain matures can be really helpful, too, in how you manage your plant size and light penetration in combination. Last year, I had a set of 4 bagseeds that finished at 64", and matured top-down. It was very crowded in there, and the bottom third did get to lookin' pretty thin. Anyway, I ended up with thick top colas, chopped them, and then dropped the light and matured the bottom half of the plants for another 3-4 weeks and ended up with a nice batch of dense thumb-sized buds. According to Subcool, maturation pattern is strain-dependent, and he didn't give a list. So, you'll have to grow a strain to finish to know which way it will go.

growth spurt that is a killer deal. please post some pictures when you receive in the mail.too bad my light only runs a hps. would i have to buy a new ballast and hood to use mh in veg? or is it just the ballast that makes the change?