I couldn't find a chart with both Kelvin and nm, in spite of how many folks seem to have asked the question, so I compiled two into one in Gimp, throwing in a few common K's for reference. I've also included the conversion formula. Interesting how nm has very little to do with the visible light appearance of the K factor... Take 2700k for instance, it translates to over 1,070 nm, quite in the black. I guess because nm seems to be based on "black body" radiation... Of course if I'm wrong about all this, please let me know how.
Can anyone confirm if this is accurate etc OP I am not saying your wrong in fact I think this is a great post that would be even better with some people coming forward who trust this is correct etc
Just for background, got the original reference charts that I combined off another MJ forum (rollitup.org); here they are: The kelvin scale: http://images.digitalmedianet.com/20...0/story/02.jpg The nm wavelength scale: http://www.giangrandi.ch/optics/spectrum/visible-a.jpg And here's where I got the formula. I did see it in plenty of other places tho... What temperature in degrees Kelvin is 450 nanometer light
It is not accurate. 8000k is Violet 7000k is Blue 6000k is Blue 5000k is Green 4000k is Yellow 3000k is Orange 2000k is Red The color temperature for vegetative growth is between 7000k and 5500k, focused around 6500k between 460nm and 500nm. The color temperature for flowering is between 2000k and 2700k, focused around 2300k at 650nm. These color temperatures, 6500k and 2300k offer the most energy in the wavelengths that chlorophyll is the most reactive to. I did this same exercise years ago. You should know that your chart is wrong when it says an orangish colored light bulb is supposed to be far infrared... Color temperature is helpful but only necessary if there is not a PAR measurement. CRi is actually pretty useless info for growing, but higher is typically better.
I think the Kelvin and nm scale may be talking about 2 slightly different things. Kelvin is temperature, nm is intensity. Then we have spectrum and wavelengths, which are also related to K and nm... Aack! Read on for this explanation I found: "The surface temperature of the sun is about 5780 degrees Kelvin, so the peak intensity of solar radiation is about 501 nanometers, which corresponds to the blue-green region of the spectrum. The sun's actual color is white because the range of wavelengths it emits is broad. The sun's light appears yellow to us, however, because of the way Earth's atmosphere scatters light." Then there's those situations that don't seem to conform to the formula, such as this Coralife light By the formula, 10,000k should correspond to about 290 nm, but they say 420 nm. Go figure...
when you are dealing with the color of light that the plant actually uses, wants, needs, prefers...cri is very useful and you want 80% or better. the best smoke I have ever grown was under 2700k (yellow) with about 5% supplement of 6500k (blue). absolutely frosted to the point of it being useless to clip the leaves off. lighting is this simple. I am currently designing efdl lamps and their applications. courtesy indagro: Definitions of the various parameters used for the 5 specification techniques o Absolute Values: These are the actual values for the lamp wattage rating shown for each of the 5 defined categories. o 400-520 (V): These are the absolute values for the Vegetative (V) region (400 to 520 nm) only. o 520-610 (C): These are the absolute values for the Carotenoid (C) region (520 to 610 nm) only. o 610-700 (F): These are the absolute values for the Flowering (F) region (610 to 700 nm) only. o Total 400-700: These are the absolute values for the Total PAR region (400 to 700 nm) only. o Efficiencies: These are the Total values factored on a per Watt consumed basis. This value generally represents an overall efficiency rating for each lamp technology for each of the 5 types of measurements and can be compared one to one since they have all been adjusted for consumed wattage. o Percentages: These are the percentage breakout of each of the 3 regions V, C, and F to the Total. The values can be used to make one to one comparisons of the different lamp technologies for each of the 5 measurement techniques.
I don't think they really correspond. For example if you look at your top value 6500k corresponding to 446nm. In a 6500k bulb most of the spectrum from infra red to ultraviolet is present but the bulb is designed with a bias to blue end of the spectrum. Of which only some of the wavelengths are absorbed by the plant. It could be useful as long as people realize that a bulb of a specific temp on the kelvin doesn't correspond to a specific wavelength. Besides I'm not really sure why you need to convert them any way...? Going by your chart a 5500k light should green but it isn't, it's pure white because it contains a balance of the wavelengths.