4 plants, 4x4 space, currently about 8 inches tall and 5-6 nodes. They have been running under just a 400 watt MH light. I just transplanted them into 2 gal buckets from solo cups (admittedly a little late, but not rootbound). I added a 400 watt MH light and a 350 watt led light (Advanced LED DS350 XML). If I add one more 400 watt light (either mh or hps) will it be too much? I know people say you can't have too much light. I have my temps controlled in the room and I can hold my hand on the cool tube glass forever without it feeling anything but warm-very warm. I should add I'm not buying more lights, it's just what I have laying around and would like to use it if it'll help.
1000 watts of HID is pretty much maxing out a 4x4 canopy area. You will know if light is too intense when you see apical chlororosis or bleaching of tissue closest to light source. Too much heat will fry the tops making them crispy. Sent from my SM-N900V using Grasscity Forum mobile app
As long as you have no heat issues, you can give them as much light as you want. The more light they have, the faster they will grow.
Best thing to do would be get a PAR meter and test the lights Umol readings at the top of the canopy. Typically cannabis plants need around 700 umol to flower apropriately. There are 3 elements to the efficiency of photosynthesis, light intensity, available co2, and temperature. With more CO2 plants can use more light, without added CO2, plants will actaully decrease their efficiency at the "light saturation point". This "ratio" also takes into effect temperature, so at higher temperatures, photosynthetic efficiency is reduce as well as too low of temperatures, no matter how much or little light is present. So to be completely sure, a Par meter would be your best bet. Just based on what you are running in your 4x4, you should be getting some good buds.