That seems like a bit of a contradiction to me. If "K rating" has to do with color, then why is that any different than "spectrum", which relates to color also.
wattage vs wavelength spectrum
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That seems like a bit of a contradiction to me. If "K rating" has to do with color, then why is that any different than "spectrum", which relates to color also.
Spectrum relates to the individual light wave lengths that are put out by the bulb (or other light source). K relates to how the human eye sees the light in its totality. Common cool white has a high percentage of light in the green spectrum. The human eye does not distinguish the green wavelengths.
Kelvin is actually a temperature rating. It is used somehow in the rating of color in bulbs though. Although I have noticed that (visible) colors seem to vary from brand to brand within the same kelvin rating.
http://en.wikipedia.org/wiki/Color_temperature
I'm not sure what you mean about the green wavelengths. They are well within the visible light spectrum.
UH well I'm not exactly what you are saying here so I'm add a bit.
Color temperature in kelvin refers to the color emitted by a black body radiator. That means that the color of the light source matches the color temperature in kelvins of heat. So a 6,000 K bulb is the color of a radiator at 6,000 degrees kelvin. If it isn't compared this way differences occur and consistent color measures can not be achieved.
Spectrum refers to the waves that compose the light; or waves that compose anything really i.e. light, sound, magnetic etc. So we should refer to the spectrum of visible light being all the colors we see naturally with our eyes.
So match the Color temperature to the appropriate region of the world to achieve a natural light. That is to say areas at the equator get a much different K rating that areas around the North Pole.
Spectrum typically refers to the colors present in light. This is important because plants, or more specifically photosynthesis, does not use all colors equally. Photosynthesis can use light in the red and blue spectrum more efficiently than all others. Those "special plant bulbs" emit light in the red and blue spectrum more that standard bulbs.
My point exactly. The kelvin rating of these bulbs is nowhere near the often suggested 5k to 10K. The black body when heated to 6500K emits a light at 1 wavelength. Flourescent bulbs emit light at a combination of wavelengths that to the human eye appear as the same color temperature as the black body.
Green is well within the visible light spectrum, what I was trying to say (very poorly) was that the light does not appear to be green.
The bulb's colors peak at the K rating. In reality there are many more colors present. So when a bulb says 6500k or 10,000k that is the most radiated color. I guess you could measure it nanometers for wavelength too.
Don't forget the distribution is not even or unimodal. They can be spread over a long curve or clearly bi-modal distribution like the grow-lux bulbs red and blue spectrum.
Also different spectrums are absorbed at different depths in the water. The longer wavelengths will be absorbed more quickly (red) than the shorter wavelengths (blue). This means that blue will penetrate the deepest and red will penetrate the shallowest.
Why are you mentioning the green spectrum??
The K rating is a useless measurement in terms of plant growth. The plant grow bulbs have a lower K rating because they do not have a huge spike in the green wavelengths like most regular bulbs do, so they appear dimmer and cooler because the human eye is most sensitive to the green wavelength. The green wavelength is the least beneficial to photosynthesis, which is why the plant grow bulbs don't use it.
The K rating is an approximation of what a black body would look like if it was heated to a specific temp. The bulbs we use are not heated to that temp, we are simply mixing colors to imitate the color temp and depending on the manufacturer, the mixtures can be different to achieve the same goal.
Chances are any fluorescent bulb that is mostly white will grow plants about as well as any other. Don't fall for the marketing ploys, those plant specific bulbs are likely no better than the generic bulbs at walmart. On the other hand, if you like a color, don't be turned away because people say the color temp are not ideal for plants. There is no ideal color temp for plants.
The K rating is an approximation of what a black body would look like if it was heated to a specific temp. The bulbs we use are not heated to that temp, we are simply mixing colors to imitate the color temp and depending on the manufacturer, the mixtures can be different to achieve the same goal.
Chances are any fluorescent bulb that is mostly white will grow plants about as well as any other. Don't fall for the marketing ploys, those plant specific bulbs are likely no better than the generic bulbs at walmart. On the other hand, if you like a color, don't be turned away because people say the color temp are not ideal for plants. There is no ideal color temp for plants.
