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A very basic lighting question

OldManGrower

OldManGrower

New member
Is it better to have your light suspended higher up at high brightness or lower down at a dimmer light level, assuming that the canopy coverage will be the same in each case?
 
Hmmm not so fast with my answer got me thinking dang it :funny: I've not burnt nor bleached bud yet. I'm still going to say i've got mine dialed down to 75% at 30" now. When my plants are in flower i'll move them closer to light till there 18" away and i go 100% on brightness. It's a 250watt from the wall.
 
It depends on a few things. If you're trying to save electricity then dimmed down closer to the plant is better but you tradeoff the footprint the light gives off by concentrating it on a smaller area. If you run the light at 100% you can raise it and you'll get more light spread across the canopy but, again, depends on the light size and power and the size of the canopy you're trying to light.
 
I tend to take roots' approach.

My lights are currently running at 45% and height is about 29" and 31".

I am running them at 45% as it brings the room up to or really close to temp without the need for heater or AC to run unless ambient is really cold or really hot.

I'll try to manage it this way for a while as ambient temps are dropping. I won't need full light until after I have harvested the autos and flipped and stretched the photos well into flower. I may need to buy another grow light once I've scrogged these photos as they will be rather large and spread out. Perhaps an SE7000
 
Great question. It seems like its an issue of light spectrum vs light intensity. It makes sense to me that spectrum is more important than intensity. If that's the case, hanging the light lower with less intensity would seem to be less stressful and would produce happy plants and good yields. But IDK for sure. Last grow I followed the manufacturer's recommendations for distance from canopy (24" veg & 18" flower) and used the dimmer to keep from burning up my plants. Didn't get a good feel for it though cause the 100% sativa plants grew into my light with nodes too far apart. The dimmer was set on no more than 5 during veg, and 7 of 10 clicks during flower, so 70%? The yield was good . That makes me wonder how a lower vs higher light intensity affects node spacing. I didn't have the environment dialed in, the difference between day/night temps was to great and that contributed to the node spacing, but I don't know how much. Imma fittin' to find out though cause the next grow has started.

This convo makes me wonder if I need to go ahead and buy a light meter as several have suggested.
 
I'd recommend running lights at 100%, as you'll get greater penetration and spread especially if you have lots of bud. I'd avoid it if you can't do it without heat problems or light stress because of ceiling heights
 
Light "spread" or "area coverage" are not an issue for me as my light completely fills the inside of my tent. Penetration into the canopy could be an issue but can be dealt with via LST and defoliation. Just wondering if anyone had figured this out. Nebula/Sirius, would this be an experiment you could do?
 
Well typically the higher the light, to a point, the more even the spread. If you go to websites like MIGRO or DrCoco and a few others that use proper testing methodology you can see what lights do and how it effects spread etc...and how wonderful reflective walls are
 
I would check that spread with a light meter. What looks like adequate lighting will surprise you once you measure the light energy actually hitting your meter.

Typically you get a hot spot in the middle with a significant drop off towards the edges.
 
Rootsruler is correct. But the concentration of the light comes into play also. I'm a 100% after flower start kind of guy. In veg I'll give them 50-75%. Then adjust height as needed. The higher the light the more the coverage you just have to listen to the plants for what is too much.
 
Rootsruler any recommendations on "good enough" light meters? Doesn't have to be accurate within +/- 1 photons. Just has to be reliable. I'm on the hunt for an infrared thermometer too.
 
Apogee are used industry wide but costs are high compared to a phone app. If you can calibrate the phone with a light meter or against the known output of your light it's good enough to start and then fine tune to your plants liking.
 
Agree. If I was testing out light rigs for a large commercial grow then I would invest in an Apogee meter but for a small tent grow I think a light app is more than sufficient. I have an android phone so I use Tent Buddy. If you have an Iphone you can use Photone.
 
I usually don't run my lights higher than 80% mainly to save on electricity but also to extend the life of the diodes on the grow light. (That's why I'm looking into extension cables for the ballast so I can mount it outside of the tent and off the board, decreasing the heat further and increasing longevity. Because I don't go higher than 80%, I do a lot of lowering and lifting the lights to give the plants the proper PPFD and DLI .
To test my PPFD, I use the Photone app on my S23 Ultra. It matches the par maps at suggested hanging height. I mentioned the app a few month back and a few ppl on this forum mentioned they too had compared their results with manufacturer PAR maps and found it to be accurate.
I haven't had any issues with light stress and I've been able to push plants up to 1200 PPFD and 55 DLI (with CO2 of course)
 
I have the same phone and app. It works good enough.

I run my lights a bit higher and brighter as I'm in a room not a tent and aren't getting much reflection.

Last grow I had my two SF7000's way too close together.

I'm running 4 autos and 4 photos this grow and I may need another light to see the photos through if I can get the seedlings to root.
 
Rootsruler I don't keep it in the tent. I keep the CO2 up in my lung room. It's a small 10x12 room with 7ft high ceilings. I just go in there for an hour everyday.... Do some exercise, tend to my plants, do some writing, or whatever. The PPM stays at least 800 in there but I try to keep it around 1200ppm. If it gets too high or a want to refresh, I just open the door and some windows and I get fresh air in. As long as I have 800ppm I know I'll get a big boost in growth with lights at 80% vs lights at 100% and ambient CO2 levels.
 
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