Optimal Distance to Light?

[Miggs]

Hi Farmers. I am trying to determine the proper distance to have between the hoods and the tops of the plants.

A little about the room:
Flower room is a sealed 12x10 with 4 1000w Ushios in assorted hoods on dimmable Phantom ballasts. 4 plants per light in 5 gal smart pots and promix. 2ton mini split. Bottled co2 controlled by a Sentinel chhc-4. Dehumidifier for lights out. 4 oscillating fans at canopy level and one fan blowing up thru the canopy at each hood.

I currently have the hoods about 8" from the glass. Temps at the canopy, measured by the Sentinel, are 80-82 lights on with 50-55%rh and 1350ppm. Lights out 68-72 and 50%rh. I feed about every 5 days at 850ppm. Nutrients in flower are Hydro-Grow, Potassium Nitrate and molasses.

A lot of the reading I've done suggests that I would get better results with the lights further away from the canopy. Thoughts/experiences?

 

[bonkia]

Personally, I have my room dialed in so I never move my lights up or down. they grow up into the light if I got a couple shortys ill even the canopy with smaller pots to add hight to the required lvl. I get a little over a gram a watt. If you look at the large ops in Canada the lights appear to be 4-5 feet high at times. Also very strain dependent sour d hates to much light. Blackberry kush you could set the bulb on and it would love you for it.

 

[bonkia]

Is that sour? Looks like it 0.0

 

[Miggs]

Thanks Bonkia.

I have noticed that most of the larger grows I've seen pics of have had the lights quite a bit higher than mine. Makes me wonder if I'm missing something.

It's a mix of Blueberry and Deadhead OG with a couple Plushberry and Lemon Skunk for variety.

 

[iscrog4food]

Many people will raise their lights to take pics. That said I use the back of the hand test. put your hand at canopy level and if it feels like you wouldn't want your hand there for longer than a minute or so then it is too close.

 

[purpleberry]

I kinds agree with bonkia, I really dont move the light much sometimes not at all ,start 4-5' away and they grow up towards the light. I use to try annd get lights closer, as some will say as close as you can without burning them. I dont really agree with this anymore esp if your bare bulb and have cross lighting. It seems diffreent hood have different sweet spots for how far away you should be. Yours appear to close to me and is concentrating the light in a smaller area, I think youd be better off a little higher.

 

[ttystikk]

In stark contrast to the casual approaches above, I feel that the distance to the light is one of the more important aspects of an indoor garden. Putting short plants in and letting them simply grow up towards the lights is a decent start, but fails to take into account strain, timing, heat, and stretch into account. At least it's going in the right direction, but in general you want to start the lights well up off tender newbies, then slowly reduce the distance over the next few days or a week. Peak intensity at closest distance should happen at peak bloom, then back off a bit near the end through flush.

This is where the biggest efficiency gains are to be found in most indoor gardens, so pay careful attention to your plant to light distances!

 

[alpinehi]

As long as you can monitor the heat, you should have your plants as close to the lights as possible in order to maximize the use of your lumens. The exception being when they are seedlings or small clones in which case you would be using a lower intensity light. GW Pharmaceuticals did a study on cannabis and found that there is almost no amount of light too great for them. In fact, they found that light levels will be harmful to humans far before they will be harmful to cannabis plants. Pretty incredible.

 

[CelticEBE]

Leaf temps are a big deal...especially when you are running co2 as I see you are. You say your canopy is 80-82.....but have you checked with a laser thermometer? Probably the best 30 bucks I have spent on growing.

Also, some strains don't like too much light...while others thrive from intense lumens. There is not SET distance.