I know the rule of thumb is 18-30" to keep hps lights above the plants and to make sure the heat is not bad at the tops of the plants. What is the main reason for this amount of space between? Is it that bad for a hps light to b closer to a plant even if you can keep the heat off of them? Figured this would b a good question for the beginner forum.
Having the light too close will bleach the leaves, even if temperature is not an issue. Apparently the leaves can only take so much light. I've found that with my 400W HPS, the tops can be about 6-8 inches away from the glass in the reflector and still be happy. That's probably about 12" from the bulb. OS
Yup what he said. First issue is the heat, but if you can remove the heat the next is light photobleaching. About 12" is the closest I've got with 1k in a hood.
when my plants get about 4-6 from my 400w is when I raise my light. I kept my 1k at least 12 inches off the tops. i have a 250w that I have had dropped down in the middle of my plants that was just a couple inches from some of the vegitation.
Is this bleaching of the plants more noticeable at the end of flowering? I got a plant that stretched up but I super cropped her and a week later I noticed the plant leaves looked like they were bleaching but up to that point the plant leaves looked good. Was not sure if it was pest prob (was due for a pest strip change). but now you all mentioned the light bleaching. Has me thinking.
Yeah, intense light will bleach the hell out of them, as well as the heat factor. My HPS stay backed off for coverage reasons, but I have had that problem with clones on several occasions. Took me a while to realize that too close is not good for fragile clones, even with CFLs. Be Cool, CG
I hang my lights ( 600 hps ) vertical and they are about 6 inches from the top of the plants with no problems.
Youll know its light bleaching as the bud or leaf will turn white. No other issues just lose of colour.
I'm with you guys. Don't think I've seen more than one case of 'slight' light bleaching, ever. Even on some 400w cool tubes with plants growing up against it. Might be different with you 1K guys, but even on my 600's the plant will cook before it bleaches. Not saying it doesn't or can't happen. Just that methinks it's less common than we believe.
I have had it where I moved a leaf and there was a perfect imprint of green. Looked like someone sprayed yellow painted on the leaves like a stenograph. I was using 1000 watter.
