This has taken on a life of its own!
Firstly the details I was discussing before, the projects side by side and the results differentiation...
The experiments were exactly the same in a sealed environment, the differences weren't massive, but there were differences. The "Bods" put this down to 2 things, 1 was shift in output, even between "identical" lights, and 2 was actual power output.
I'm not going to name names, but the LEDs used were from a huge dutch corporation who seek to control everything in the LED industry...and their product and ALL of their research initially was around the red blue spectrum and providing supplementary light for glasshouses, therefore their actual outputs didn't nearly so much matter, in fact in one research facility I've been into they don't actually know how much these new generation versions are contributing, simply that they are saving power and getting some favourable results.
In this instance growers usually have sealed environments, so the power and output is EVERYTHING! So for example, when we got involved we had some very rudimentary test kit, and we quite literally tested everything we initially received and threw it away when we considered it against another (very good but very expensive manufacturers kit), we were't in the game at producing a generic faddy light without some data behind us...
Anyway, so COBS!
There are some horrendously bad chips out there, there are some average ones, and like anything there are some good ones...we tested quite literally hundreds of variants and we initially (and still do) have made a proprietary red/blue for supplemental light, we include either a phoshor or a natural (around 4200k) white for our commercial clientele...BUT for you guys the flowering stage is important, so we worked with our manufacturer (a very large concern) and came up with a phosphor chip which is doped to a curve, this curve is what we developed with the research partners we have, is used in almost all our research work and is unique to us, phosphors are starting to appear here and there, but they are a generic, indeed we take some of the information we get and "tweak" our spectrum slightly every time we order a new batch (we order a production run maybe every 6 months depending on sales and they last a year usually).
COBS in general are efficient, but to use a white chip would be erroneous, the simple fact is that a plants response curve requires bits of this and bits of that sometimes in line with what a white cannot provide...I'll try to provide a graphic later showing the curves overlaid...we have a natural white and at the moment, that cannot "do" everything so we're working on an "altered state" white but we're probably 2 years from having a product we are happy with.
So in general, COBS we feel are the only way you can generate the power required for penetration in a canopy, in that particular sector we feel that a multicoloured chip with individually coloured diodes is very difficult to get an even response curve from without having HUGE lights and many different power percentiles, (remember some wavelengths are just inefficient) or take an efficient blue chip (the colour most LED is to start with), dope it with a set "curve" and electrically you have an efficient chip, with a compounded spectrum curve and overall if used/focused correctly enough power to penetrate a canopy giving even penetration.
HOWEVER, this forum is about how to buy an LED light, the basics if you will. Our theory is well documented, the website etc will happily explain it. BUT overall, I would say that if you buy any LED light, make sure that with your chosen light AT 60cm above floor level your chosen supplier of light should be able to give you a guaranteed minimal 215umols EVENLY around your grow space. Diffuse, even light is more important than anything else and you feel happy with your purchase. If your chosen manufacturer cannot provide you with a recent and averaged umol test for what they are trying to sell you from a non reflective chamber, then they are selling you snake oil...and they know it...
Inverse square law defines how light travels, so effectively an "at source" measurement means nothing...and bouncing LED through or around with mirrors really doesn't work...
