"Not an expert" myself, Fred, but I get frustrated searching the internet for lighting info, and all the "expert bloggers" just keep saying the same thing; "lumens are for humans" and while cute, repeating that isn't a standard for us. All the "cheap lights" don't give you the real specs do you can judge their lights. I found the new UL specification, UL8800, for rating horticultural lights, https://ul.com/services/horticultural-lighting/ "UL 8800 is used to evaluate horticultural lighting equipment from manufacturers seeking the UL certification Mark for their equipment and devices, and as of March 2021, the DesignLights Consortium (DLC) requires UL 8800 safety certification" While the specification report example at thst link is obviously designed for people better trained than myself, I can certainly understand the main UL 8800 standards goals: -insure the wiring and fixtures are safe and secure. -insure the fixtures are reasonably moisture-proof, and meet minimum standards for dust, uv and heat protection. -insure the light output is safe enough for humans- our eyes and skin- to be sharing the growing space -and finally, insure the light output is correct wavelength and efficent for the plants. About wavelength: while the internet indists "red/blue" is all the plants need, the UL specification detail PDF from that link says its reports will provide" 350-800nm spectral distribution, acknowledging chlorophyll is not the only photo reactive chemical in plants, to illustrate a better picture of what light output a product is providing." So, maybe the purple lights are a little behind the curve, being edged out by the full spectrum crowd? I don't know, but I'd love to hear more educated answers from this list... It also shows the recommended height and spread of each rated fixture, so you can judge if your lights are producing the desired intensity your plants will respond with. The problem is manufacturers desire to qualify for this new standard. I guess that's where we come in... demanding a standard before we purchase? Ken _______________________________________________ pbs mailing list pbs@lists.pacificbulbsociety.net http://lists.pacificbulbsociety.net/cgi-bin/… Unsubscribe: <mailto:pbs-unsubscribe@lists.pacificbulbsociety.net> PBS Forum https://…