Light Advice

[hycheese]

Hello all, I feel like I know most of you already since I pretty much read this forum cover to cover for several months before registering. So far my only mistake was not thoroughly reading up on the LED lighting requirements as I was only planning on doing one plant at a time.

I am germinating 2 northern light autos from Nirvana right now and am worried I may not have enough light. I did some light measurements with a cheap LUX meter and these are my results; The Hybergrow was listed as a 300-watt equivalent. below is the actual watts/lux.

40 watt cfl @4" = 15,000 lux for the seedlings
6 watt cob @4" = 35,000 lux, @8" = 12,000
100 watt @8" = 30,000 lux, @18" = 12,000

NL autos - hopefully short.
4 gal grow bags 60/40 coco/perlite washed and buffered.
2'x 4'x 5' high grow table lined on 3 sides.

 

[DrPhoton]

Single lux measurements cannot tell you the total light output capacity of a light source. So one cannot judge the efficacy of a light source by these metrics alone.

Off some simple calculation, using generous photon efficiency values. I estimate the main lights to provide something equivalent to about a 300 watt sodium discharge, combined.

Your fluorescents are satisfactory, though you may find you will have to raise them if you start seeing bleaching symptoms. I have performed various experiments which show that if seedlings are provided more than 5000-7000 lux, they typically have slower growth and show signs of stress. Some strains handle better than others and how well you propagate can also have an effect on their ability to tolerate excess light. However, 5000-7000 lux seems to satisfy most conditions and strains.

I have plenty of articles on subjects of plants and light, the one on using light efficiently may interest you. Any questions feel free to ask.

 

[hycheese]

Thanks for the info, I read all your articles on light - good thing I read Richard Feynman's book on Quantum ElectroDynamics 20 years ago or I would have been lost.

 

[DrPhoton]

Nice, your ahead of me then on the physics of light. I only learnt enough to make sense of the fundamentals. Its certainly fascinating how complex light is in nature. Working with coherence, polarization, wave characteristics, particle behavior etc. Its certainly not simple ^.^