Quote Originally Posted by khyberkitsune
I think that is a good approach and is great data - allow me to toss out another approach.

First, I kept in mind that plants pretty much adapted to their lighting environment. Light levels and spectral balance is somewhat important. Next, for the boundary between spring and summer, I checked with NASA records to check the insolation levels recorded at the edge of the atmosphere and at the edge of sea level - I noticed the balance, at least in terms of radiometric power, were almost even - blue was in the lead. Then I checked again for the beginning of September (bear all of this is for my old area, in Tennessee, I haven't checked to see if there has been any data for my area of Cali.) The ratio had changed , with red slightly in the lead. So I figured a 60:40 blue:red mix for vegetation, and a 60:40 red;blue mix for blooming. I might modify the panel once it arrives, see if I can't drop a dimmer on the blues so I can drop the blue down to help trigger flowering, and then bump it back up a little to provide some extra boost. I've always had poor yield results, especially with tomatoes and peppers, with those 7:1:1 panels. More blue is needed. Other lighting companies realized this and are starting to offer blue-dominant panels to supplement their lacking UFO panels. NASA realized their folly and some of the latest panel design I've seen from them is pretty much 1:2 blue:red (looks like 465 and 670nm.)
Are you growing space-weed? What does the solar radiation at the edge of the atmosphere have to do with anything? I don't think the relative intensities of different wavelengths of sunlight have anything to do with it either. As green and yellow are also more dominant wavelengths than red, your logic suggests you should add lots of those to your LED array. Let me know how that works out.

Where is this stuff saying blue light is better for driving photosynthesis? All the studies I've read say that photosynthesis only occurs at around 50% peak rate on blue light alone - the peak being around 670 nm. Blue light is only required for physiologicial and morphological responses. Again, all the studies I've read say between 8 and 20% of your light should be blue - depending on the plant. Also, flowering is a phytochrome response. It is triggered by the length of the dark period - not by the blue:red ratio of light. Weed is a short day facultative plant. If you have long dark periods you will be able to accelerate (or short nights will slow) flowering but it will eventually flower regardless of the light color/duration. I really don't understand why so many people have this misconception. Show me this latest NASA panel design too. I might have to eat my words here in the next few days. :P