Why 30" From Light?

I have good uva/b sunglasses hanging right there. Just part of the Rules. They are also for handling bases and acids. Same rule, really.

I'm a hobby torch welder, oxy/acetylene, would the goggles I have be tuned properly to protect from this type of light?

I use my Ray Bans or Oakleys. Just be especially careful with MH, as it can emit really strong doses of UVA & B if the inner uv filter is damaged.

ProdigalSun said:

Is bleaching the first symptom of having the light too close?

I don't mind moving the light away, if it's going to help my plants but it seems to be counter intuitive to do that when I just spent money to get more light by upgrading from the 600w to the 1kw light.

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1000w is going to give you more penetration. A plant can only take so much light, your tops are going to get that. Now the middle of your plant will get more as well.

amgprb said:

Even the hand test is only an indicator. My 600 cooltube, i can keep my hand 6" away without any issues. I think that is more for heat stress issues. I dont know if there really is any sort of "test" for light toxicity

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You are right the hand test is a indicator, and a good "simple" rule of thumb.

Not everyone wants to buy a light meter from Hydrofarm, wait. I got one those.

I like science, I like tools that measure because I like to try and control as many things as possible.

I got the meter after I got the Bleached tops, the lumens under my hot spot were three times higher than under outside edge of my hood, that's when I raised my hood and tilted the hot spot side up so the lumens were more even across the whole plant.

by the way I think the light meter is worth the money but that's just me.

ProdigalSun said:

I regularly see people posting that they are keeping their 1,000 watt lights ad distances of 20 or 30 inches from the plant tops. Why do people do that? I have a 1kw HPS and the plants (including a sprout from day 1) are about 12-14" from the center of the filament within the bulb. My temps are in the mid 70's in the room, and the area right at the plant tops is never allowed to go above 85*F.

So Why so far away?

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Same reason street lights are on 30ft poles. We use higher wattage bulbs to cover more area, not hit them harder. Hell at 50 watts per sq ft. all you need is a 50 watt floro if you are only lighting a square foot. You can have that 1 inch over the tops!

ProdigalSun said:

I have never experienced any bleaching, even under a 24 hour schedule, what does that look like?

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There ya go.

Well, anyone with a light meter can tell you that lumens can diminish at a certain distance. I recently read in a magazine, a guy who owns a grow store that tells everyone to "tale their light as high as it will go, and leave it there". He said then they will tell him, "that's like 5 feet above my plants" and then he says, "yes". And waits for them to say something. He then tells them "not enough light is NEVER a problem. Too much light is ALWAYS a problem.

I totally disagree with the statement. Not enough light can result in stretch, shitty growth, airy buds, etc. But at the same time, it really can go both ways.

I think it all just depends on your setup. If you have cooler temps you can totally get away with running it a little closer, I've found. But like for me personally, I just moved my magnum xxxl hood and 1000w from a 4'x2' tent, to a 5'x5' tent. The hood itself has a huge footprint; it actually barely fit in my smaller tent. I kept it close (with the help of an air conditioner) but still had some problems going into flower with my tops yellowing on me. I attributed it to pH swing, but now I think it was too much light.

Now that I am using the 5' x 5' tent, I have a short plant in the middle, it's probably 25-30" from the bulb, but other taller plants around the outside that are a little bit closer. I moved my light higher so that the footprint would get bigger, and I've seen a lot better health of my plants for the first part of flower. In fact, its looking like I'm due for my best crop ever if everything keeps going smoothly.

In conclusion, too much light can definitely fuck your shit up. Too little light can leave you wanting when you go to crop out. Find the medium that works best for your environment. When you do, everything comes together nicely.

ThorGanjason said:

View attachment 2935963 There ya go.

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Thanks, I would have guessed Zinc.

Im guessing that certain plants are more susceptible than others to light burn? I had the tops of a plant do that a couple months ago, and couldn't figure out what I had done wrong. I was having some bad ph and bad water issues so I figured that was it.


Lights going up.

Yeah, if you saw a picture of the whole plant you'd see its only on one part of the plant so its pretty easy to spot.

I got it from t5's, which is pretty hard, they almost have to be touching it, really. But I have a tall blue dream on one end and a tall purple wreck on the other end, so I try to keep them close for the two plants in the middle. Plus the growth is so fast in that aeroponic system I gave to move them everyday. And yeah, I'm sure certain plants/strains are more susceptible. "Desert" origins plants prolly handle it the best.

I

have a 1kw HPS and the plants (including a sprout from day 1) are about 12-14" from the center of the filament within the bulb

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Directly under is hottest. I have a 1000w with cooltube and plants are as close as 5-6", no burn, roomtemp max is 27. You can have them close if to the side of the light not right under.

Now that I am using the 5' x 5' tent, I have a short plant in the middle, it's probably 25-30" from the bulb, but other taller plants around the outside that are a little bit closer. I moved my light higher so that the footprint would get bigger, and I've seen a lot better health of my plants for the first part of flower. In fact, its looking like I'm due for my best crop ever if everything keeps going smoothly.

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I think the closer is better myth has caused more problems than just about any other single item in your indoor grow. I know I bought into it 100%. I had water cooled lights that you could have 2 inches off of the tops if you wanted. Took me about 3 cycles to see that my best results were coming from the plants that were 30 inches away. Always stressed plants with too much light which invites all sorts of trouble. For me, success came only after I shed all the complexity, bought a big AC, opened the hoods and raised them to their optimum height. Been smooth sailing ever since. Keep in mind we are talking 1k hps here.

My plants are already doing better, what a surprise, thanks guys.

Hey, what's the best distance for the 400w, and 600w bulbs since the topic is still hot. The info could prove useful to a lot of growers, and I can't do the math. Thanks.