hello all. if you've noticed on the carton of just about any HID horticultural bulb there is a color graph showing the bulbs "wavelength in nanometers". so i'm wondering how this relates/compares to the color temp of the bulb. the highest "peak" on the graph on my MH conversion bulb is at 625(ish) nanometers and on the hps bulb the highest peak is at 570 (ish) nanometers, but there are other peaks on both bulbs graph. this is something i've been wondering about but haven't found an answer anywhere. thanks in advance.
They are best viewed as two different things. Color temperature is a measurement which basically means, a theorectical "blackbody radiator" heated to this temperature, would produce the same color of light as the chosen source (i.e. a lamp). Basically, sources with higher color temperatures have maximum intensities at shorter wavelengths (those nanometers). In other words, the higher the color temperature, the more blue it is. A low CCT (say 2000K) would have maximum intensities in the longer wavelengths, and would appear more red; ideal for flowering. Only sunlight, carbon arcs and incandescent (tungsten filament) lamps can give you a "true" color temperature reading, and the term can't be accurately applied to HID lamps. Color Temperature for HID lamps is actually "Correlated Color Temperature" (CCT). CCT is a mean average approximation of the overall colour produced by the lamp. Think of it as a "rough guide" for HID color, no more. It does relate to your diagram, but it would take a computer to work out the CCT from all the different wavelength peaks. Those graphs are fun, though, if you plot them against the spectral response of a plant, you can see how much light is being wasted. I'll attach the spectrum from the worst HPS lamp I've ever used for growing. When you look at where the main peaks are, you can see why it was so crap. -mu
mu- thanks a million for taking the time to not only answer my question, but answer it thouroughly and in english (or at least not in technichal mumbo-jumbo). + rep for sure. am i to assume that the worst hps lamp you've used is that solarburst that's on sale for free? good to know not to ever use those.
No Problem! It was fun. And yes, if you send me a jiffy bag, it's yours! Ideal for parking lots, streetlights, or whatever, so long as it's not for growing plants. It was only eleven bucks or thereabouts, and a gift, so I can't complain too loudly. After a few days with the solarburst, my plants had barely grown 1cm, and that was during the stretch. I put back my regular SON-T (standard 45,000 lumen parking lot lamp, came free with the 400W rig) and they picked up again almost instantly. I lost a few important days of flowering growth, though. Live and learn. I ordered a Plantastar after that. A good lamp. -mu
i've been using an agromax hps/mh conversion (cheap bulb, but works great) and i've got a eye hortilux on the way (400w hps) WOOT WOOT! anywho thanks again.