Steve yes you are correct that I am aware of the lumen/lux vs ppf/ppfd, human eye vs plant. Throw in PAR too! None of these terms seem to truly help the hobbiest grow Massonia’s, Conophytum’s or Cannabis. My reason for high end LED’s is light penetration. I wanted to replace my HPS system rated at 55000 lumens. I could have went with a dozen T5HO fluorescent. However the LED’s at 325 watts made the most sense to me. This was for growing in the basement. I started with supplemental lighting last year when I saw Arnold’s results who lives in the same state as me. Arnold indicated he used supplemental lighting based on advice from Rimmer. Now I am a full member of the supplemental light club. Ha ha. I need adjustable height hangers for the lights next year. Steve noticed my LED’s are under driven and therefore are passively cooled. Heat kills LED’s. Stay away from fan cooled systems. The fans last a year or two and need replacement or you kill your LED’s. Heat is wasted energy and money. Ken P New Jersey, USA Zone 7a The past was erased, the erasure was forgotten, the lie became truth. George Orwell, 1984 > On Feb 26, 2022, at 1:44 PM, Steve Marak <samarak@gizmoworks.com> wrote: > Hi Ken, > > That is a rabbit hole, as the lumen unit is biased for how our eyes respond to light rather than how plants do or the power distribution of the light. (Your careful wording suggests you're aware of that!) > > I Googled the BML SPYDR, since that isn't one I've used. It's clearly a high-end unit with a lot of careful design and attention to detail behind it. I particularly like that they under-drive the LEDs; LEDs can last for many years if not run too hot but a lot of cheaper fixtures do that to cut cost. > > Where I use artificial light, it's the primary source, so I can't help much with it as supplemental lighting. As Leo mentioned, unless you use long-life fluorescent tubes, which cost more, their light output will decline quite a bit, often within a year and nearly always within 2. Long-life tubes hold much more of their rated output much longer, but I still prefer LEDs. Distribution is also important when considering a single higher output fixture vs 2 or more lower output. None of which addresses your question about amount of light in lumens, of course. > > Best to measure, if you can. If you have access to a PAR meter, measure the PAR flux you have now, which is clearly working, and then attempt to match that when/if you have to replace the fixture. If no PAR meter, well ... the purists will be outraged, but I'd just use a cheap meter that measured lux/lumens to get a base reading on what you have now. Not the data you really want but I don't think it's completely useless either. > > Plants are amazingly good at harvesting photons across the visible spectrum, even green ones (related geek content below), and my personal experience is that as long as the color temperature of the light is high enough (because that ensures there's some up in the blue region), there's considerable latitude in what works, even if it's not precisely optimal - which is what I'd expect. High enough for me is 5000 K, though I prefer 5500-6300 K. As Leo also pointed out, color temperature as we use it for artificial light sources doesn't mean the spectrum is what a real physics black body at that temperature would produce - that's another rabbit hole - but I haven't found spectrum to be an issue either except in a few fringe cases. > > Sorry about the length, and that I don't have better advice. > > Geek content - I stumbled on this fascinating article a year or so back: https://quantamagazine.org/why-are-plants-green-to… > > Steve > > On 2/25/2022 1:43 PM, Kenneth Preteroti wrote: >> Steve I appreciate your comments and the comments sent to the group and to me privately. I accept that the cost to benefit ratio of high end LED’s is not reasonable. I will continue to use my old BML lights (I believe they are equivalent to a 600 watt metal halide not 1000 watts as I previously stated) to supplement the sunlight in the winter months. When the BML lights fail I will look to purchase economical lights. >> >> One question which is the rabbit hole you may not wish to go down. Using lumens as a measuring unit (because that’s what is printed on the shop light box and fluorescent bulbs) a 2 bulb 4’ T5HO 108 watt fixture puts out 10000+ lumens while the 2 bulb 4’ 40 watt shop light puts out 4000+ lumens. What are your thoughts on the amount of supplemental light? >> >> Ken P >> New Jersey, USA >> Zone 7a >> >> The past was erased, the erasure was forgotten, the lie became truth. >> George Orwell, 1984 >> >> _______________________________________________ pbs mailing list pbs@lists.pacificbulbsociety.net http://lists.pacificbulbsociety.net/cgi-bin/… Unsubscribe: <mailto:pbs-unsubscribe@lists.pacificbulbsociety.net>