Let's talk 600w MH and HPS light distances

VapeItNow

VapeItNow

Member
I have studied the light distances for these lamps on the web and have not found the same distance recommended twice. The overall range is anywhere from 12" - 18". I don't believe in the hand-under-the-light idea, sorry. I have seen the charts for MH and HPS light distances. The HPS light distance chart attached says a 600w bulb can be safely placed at a distance of 8". The MH chart doesn't show the values for a 600w bulb. I couldn't get it to upload anyway, argh! So what is on to think?

I found these other charts on PAR that are very interesting. The HPS chart shows the bulb at 100% at a distance of about 17.5", and I'm guessing the MH chart is about the same if you imagine there are increment marks at every 200w between 400 and 1000.

My conclusion is that I should try to get my ideal temp at the top of the canopy with the light at a distance of 17.5". Any ideas or comments???? There must be something I'm leaving out. Would this apply to every stage of growth?



Hps_Distance_Chart.jpgHPS-PAR-Graph.gifView attachment 2561673MH-PAR-Graph.gifView attachment 2561673






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PersonalJesus

PersonalJesus

Active Member
Hey bud...
You really shouldn't go with hard and fast and set in stone rules, such as "I will always keep my light so and so inches above my plants"... Personally, the closer the light the better. I would recommend trying "the hand trick" as you put it, and set your light distance that way.
Or you can set your light wherever you'd like and just watch your plants... if they start to stretch to reach the light, move light closer... if they start to burn or get sun bleached, move light away.
Light distance is basically the same regardless of stage of growth... more light, better growth equals better plant.
Hope that helps.
 
D

DOYOUSMELLTHAT

Well-Known Member
I had my 600 mh about 36 inches for 2 week old sprouts...did that a week..moved to 24 inches...doing great...moving to about 20 inches today and making sure temp doesn't go over 75-77 and I think Ill be happy. I have an air cooled glass paned reflector with a 6 inch exhaust inline and it works pretty good for temp for my 600.
 
navyfighter04

navyfighter04

Active Member
There is no such thing as repeating the same results exactly. Its IMPOSSIBLE to do You can tweak everything and get it close but never the same. Point im making here is EVERYONES plants are different. We could have the same set up, lights, pots, soil,etc. But my strains are sativa and yours are indica. I might be able to keep my lights only 12 inches away where you have to stay 18 inches. My point being every grow is different, and will be different, every time. So dont go by what the labels say so much as you go by what your plants say....Good Luck
 
R

Rooty420

Member
Also,one more thing to consider is the bulb itself.Some bulbs greatly outperform others.I also have heard older bulbs get hotter.
 
VapeItNow

VapeItNow

Member
Thanks so much for the input everyone, and I understand what you're saying. I can see where every grow would be different because of the condition of the lamp, the strain being grown and the variables in the grow room. What I think I'm hearing, is to always check the temp at the canopy level and watch how the plants respond to light placement.

My seedlings are one week old now, and will need to be transplanted in another week I'm guessing. Around that time I will have the tent setup. Will it be too much shock to transplant, nute and put under the new MH light at the same time?? It makes sense what DOYOUSMELLTHAT said about gradually moving the light closer on seedlings.

Thanks for your help!
 
navyfighter04

navyfighter04

Active Member
VapeItNow said:
Thanks so much for the input everyone, and I understand what you're saying. I can see where every grow would be different because of the condition of the lamp, the strain being grown and the variables in the grow room. What I think I'm hearing, is to always check the temp at the canopy level and watch how the plants respond to light placement.

My seedlings are one week old now, and will need to be transplanted in another week I'm guessing. Around that time I will have the tent setup. Will it be too much shock to transplant, nute and put under the new MH light at the same time?? It makes sense what DOYOUSMELLTHAT said about gradually moving the light closer on seedlings.

Thanks for your help!
Click to expand...
Ok, to your question on the stress. Yes it would be too much for the seedlings to do all that right away. Transplant them, and wait a week before feeding nutes. First of all the soil you transplant to will have nutes in it. Most soils will give you 3-5 weeks of nutes before needing anything added. Keep that in mind so you dont burn them. Second the MH light will be ok, but keep it up enough as to keep the tops of the plants cool to lukewarm. You dont want to burn them....Good Luck
 
SoCal88

SoCal88

Active Member
It also depends on what kinda cooling you're doing with that light. I use to use a 600 hps (I flower outdoors now) for flowering. As long as I had my 400 cfm fan cooling it I had no heat issues at all !!
 
garagiste

garagiste

Member
I think you can get into trouble if you try to get the lights as close as possible without burning. You can give the plants too much light and if you have a single source the closer you get the less evenly the light will distribute. It isn't just worrying about burn. My last grow was done in a cold garage and I could get the lights really close, like 6 inches or less, and had 7000 lumens nominally per square foot and five light sources. Never had burn, but the plants stayed light green color no matter nutes or watering. Yield was okay, but plants never looked really healthy. Moving the lights back give much healthier and even growing plants. I keep them at least 14 inches or so away now with a combo of MH and LED. LED's on 20 hrs, MH on eight at night (when garage coldest) during veg. They look textbook great.
 
Trousers

Trousers

Well-Known Member
My 600 watt hps could be closer with out heat problems, but some of the middle plants bleach out. I like to keep it more than 12" away.
 
SourD420

SourD420

Well-Known Member
VapeItNow said:
I have studied the light distances for these lamps on the web and have not found the same distance recommended twice. The overall range is anywhere from 12" - 18". I don't believe in the hand-under-the-light idea, sorry. I have seen the charts for MH and HPS light distances. The HPS light distance chart attached says a 600w bulb can be safely placed at a distance of 8". The MH chart doesn't show the values for a 600w bulb. I couldn't get it to upload anyway, argh! So what is on to think?

I found these other charts on PAR that are very interesting. The HPS chart shows the bulb at 100% at a distance of about 17.5", and I'm guessing the MH chart is about the same if you imagine there are increment marks at every 200w between 400 and 1000.

My conclusion is that I should try to get my ideal temp at the top of the canopy with the light at a distance of 17.5". Any ideas or comments???? There must be something I'm leaving out. Would this apply to every stage of growth?



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Click to expand...
You dont believe in the hand under the lamp? Lol its far better to use your hand to see it is too hot where the canopy is rather than just putting it at a standard distance and hoping everything is ok
 
jmoneygrows

jmoneygrows

Active Member
Have to keep my lights a minimum of 18 inches. I took off the glass from my hooded hps 600 watt and noticed the top colas were not filling in as well as the ones slightly lower. Even with temps on point the tops need more room than you think. If they are stringier buds than the ones to the sides or if you see bleaching it's time to super crop or move lights. I ended up tieing strings to the main stalks and bending them down/tied to trellis net to give them an extra 3-4 inches of room. Just make sure when you do this they aren't shading smaller tops. Seems to be working.
Remember no matter what the light source (even hps lights) you can most certainly give them too much light. And despite them looking pretty unique, bleached buds have less thc.
 
jmoneygrows

jmoneygrows

Active Member
Oh and it is most certainly strain specific. Growing 4 diff strains at once under the same lights (all indica dominants) and some bleached while others thrived. So it'll be different for every strain. Just pay attention to the WHOLE plant. The biggest colas should put on the most weight. If the side ones are outperforming it means the tops have hit a light wall and have nowhere to grow into.
 
Dudemankidson

Dudemankidson

Active Member
Sometimes I check for cupping as an indicator my lights are too close to my canopy. I know cupping is a result of heat not too much light but the lights do put out the heat for the most part & thus I think why the hand under the light trick holds some weight. 2 cents.
 
boilingoil

boilingoil

Well-Known Member
jmoneygrows said:
That's great. Some can handle that kinda distance. How old is your light?
Just be mindful of top growth
Click to expand...
My light is a Gavita 600-750 DE ran at 825 watts. In a 4x8x7' grow area, so that come to around 25 watts a sq.ft.DSCN0753.JPG
Or a 600 watt HPS in a 4x4x7' grow box with the lighting fixed to the ceiling. Or around 37 watts a sq.ft.DSCN0669.JPG
In the old days we use to rent houses and hang a single 1,000 watt from each ceiling in the center of the rooms and let the plants stretch into the lights. Wasn't the most efficient way but back then we were getting 1.5 lbs from each light and with 3 rooms in each house ran like that, we would clear $20,000 per house every 6 months.
 
boilingoil

boilingoil

Well-Known Member
Most of the ones in the first pic are personal crosses. If you're wondering about the purple bitch, that's a cherry cheesecake pheno #1.DSCN0757.JPG
 
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