new screen and lights dark growth

Little late, but just so you know, cool whites output nearly identical amounts of 455nm as a royal blue. It would actually be better to use CW than RB IMO because some of the other spectrums in the whites will help in other roles of photosynthesis.

This is what I have been working on the past 6 months. This was day 1 right before plants were put in, and since then I have been tweaking the hell out of the light to obtain peak photosynthesis, to the point it now only has a few blues left, none of them royal blue (few 420's and 480's), more cyans, and a lot of warm whites and deep reds. My goal is to design as near perfect of a grow light as possible and Mfg them to sell to indoor growers. For the last couple years the push has been to just go from one extreme (all white light) to another (all blue/red light), and now today with enough people doing experiments in this other hobby, we are learning that a little blue goes a long way, and white LEDs contain enough royal blue spectrum to satisfy plants needs in the spectrum. There are other spectrums in blue that could use a boost from blue leds, and also cyan actually plays a much bigger role in plant growth than initially thought, and that spectrum is completely missing from white LEDs so adding cyans for this purpose really helps. For an algae scrubber, the layout most of us are using now works ok, but today I think replacing the royal blue with cool whites helps with photosynthesis.

 

Well, in a pinch that is ok, especially if you need to do so because you are running LEDs in parallel, but just to clarify, I am only talking about replacing royal blue with cool whites. The amount of reds that most of us are using are fine and don't need adjustment. I understand why you did it, just didn't want anyone else getting confused between my statement above and what you did in your reply.

 

Sorry Scott, last 'thread jack' by me. Since we are on the topic of LEDs I just wanted to show the 'full box' I made, different sections for different stages, using different types of LED lighting to see what works best. Second picture is a cool shot I took showing the different spectrum of LED light I started with initially on the 'vegetative' side of the box. 3rd picture is what the entire box takes to run in electricity, all lights, fans, air pumps running, and so far it has proven to be comparable in growth to 4000w of traditional MH/HPS/T5HO lighting. My goal was to create a box that can grow 4lbs of product every 90 days and take less than 400w of electricity (the typical MH used for small space grows). I succeeded by a mile. Everything is 100% legal under the laws of California, and I have no involvement with the plants that are grown or the product they create, my only interest in thiat hobby was I felt I could create a product (LED light) for which there is a high demand for in the state I live in, I just needed to prove I could do it first before trying to sell it to others (I know, very non-SM way of thinking).

 

From what I have noticed on this particular type of plant is it comes down to resin production/potency when you switch between Red/Blue to White/Red. The extra spectrums from the white LED help in many other areas of plant growth as the graph below shows, but even white LEDs have their limitations which is why on my light I added 420/480/505nm LEDs to fill in the gaps. I am just now starting to experiment with true 'Far Red', light above 700nm as there is some question as to its importance. 420nm is important, and so is 480-540nm. Royal blues have a very narrow bandwidth, a 455nm will have a +/- 5nm range. Cool whites also use the same phosphors and have the same spectral range in the blue spectrum, so even with cool/neutral/warm whites, there is still a large spectral gap from 470nm-510nm, which are very important to have. So the red/blue light, the leaves will look similar to the white/red light in texture and form, but they won't have the glossy coating and crystals growing on them.

http://plantphys.info/plant_physiology/light.shtml

 

The 'cool blue' (480nm) to cyan (505nm) is where the gap is with white LEDs and appears to be very important for overall health of plants, and unfortunately that range is excluded from most fixtures and white LEDs. Look at this chart, it shows how energy transfers through the plant. If you only provide light for the top and bottom of the chain (chlorophyll A/B) the entire chain in between becomes weak and inefficient. Like all things, plants will adapt or die, and as proven beyond a doubt by being able to grow plants under 2 narrow bandwidths they do indeed adapt, but they don't seem to grow nearly as healthy as plants with broader spectrums. Intensity of each spectrum is the key to making a light the most efficient, which is why I am changing out a handful of LEDs weekly on my 100+ LED fixture to try and dial in exactly what intensity is needed in each spectrum. To me, a huge light geek, it has been an extremely rewarding experience.

 

Just took a few pictures of the light as it is today. I have to try and remember exactly how many of what I have in there but off the top of my head these are the different LEDs used.

Blues: 420nm, 435nm, 445nm, 480nm
Cyan: 505nm
Whites: warm whites
Reds: 640nm, 650nm, 660nm, 700nm

Couldn't get the entire light in one shot, so here is left/right shots. The middle cluster of red/white lights moves around to be placed where we feel it is best needed.

 

Holy light show!