I think it is hogwash. You already said it. Photosynthesis occurs when a photon of light from just about anywhere in the visible light range except green hits a chloroplast. The intensity of the light determines the number of photons per second that will hit the plant. The color temp is just not that important.Dancing frogs said:...though I have seen somewhere the suggestion for using a 6500 or higher for broms...if anyone has any evidence to back that up, it would be nice to see.
The color temp has nothing to do with how bright it is. You can have a very bright 4000k bulb an extremely dim 20,000k bulb. You actually lose PAR as color temp goes up.mydumname said:Ouch, my eyes! My 6500k's are bright, these 1800k would probably light up my street through the window.
There are some very subtle differences in the way some plants react to the different portions of the visible, UV, and near infrared spectrum. Most of these, to my knowledge, have to do with how stem elongation or flowering occurs. But these are more of interest for commercial growers than people who just want pretty, healthy plants in their vivs. There is and exception though. Aquatic plants. Shorter wavelength light has more energy in it so UV to green has more energy than yellow to infrared. Water filters out light and the portion of the spectrum with the least energy gets filtered out first. So the blue and ultraviolet light is what penetrates deepest underwater so the chlorophyll of many aquatic plants is optimized to take advantage of that color of light. That's why reef tanks use actinic bulbs.kyle1745 said:I have read that some plants do better with stronger parts of the spectrum though. Depending on the plant. For example some need more red or blue.
Usually expressed on bulbs as lux (sometimes lumens and rarely as foot candles) All of these are measures of light output, more is better. But as was already mentioned, you need to consider the spectrum of light produced. Color temp and CRI are only indicators of spectrum. A bulb with a color temp of 5000K-6700K and a high CRI probably has to have fairly even distribution of light across the visible spectrum to get those numbers so that is good for plants. It's theoretically possible though that a lamp could produce a billion lumen of green light which would blind you but do absolutely nothing for the plants.FCA said:Yes, the Kelvin rating is just the color of the bulb. You have to take into account the CRI, PAR, and/or lumens to judge how bright it will be.
dmartin72 said:I just refuse to pay $24 for a bulb! :shock: