Color temperature is a characteristic of visible light that has important applications in photography, videography, publishing and other fields. The color temperature of a light source is determined by comparing its hue with a theoretical, heated black-body radiator. The Kelvin temperature at which the heated black-body radiator matches the hue of the light source is that source's color temperature, and it is directly related to Planck's law of black body radiation. A Kelvin rating suggests how warm (red) or cool (blue) a source of light is. Imagine a blacksmith heating a horse shoe, the shoe first glows a dim red, then an orange, yellow, white, and blue white as the "temperature" rises. Although it may be confusing at first, the higher the temperature, the cooler the color. The color temperature of a lamp (bulb) describes how the light appears when the human eye looks directly at the illuminated bulb. Color temperature is measured by a unit called the kelvin (K), a scale that starts at absolute zero (-1273 degrees C). Imagine heating a bar of steel and observing the color of the bar at increasing temperatures. At some point the bar will appear to glow a dull red. As heat is added, the dull red turns to yellow, then to white, then to bluish white, finally to blue. A light bulb that produces light perceived as yellowish white will have a color temperature of around 2700K. As the color temperature increases to 3000K - 3500K, the color of the light appears less yellow and more white. When the color temperature is 5000K or higher the light produced appears bluish white. The color temperature of daylight varies, but is often in the 5000K to 7000K range. When the desired lighting effect is "warm", use light sources in the 2700K - 2800K range. Most common incandescent light bulbs will produce light in this color temperature range. An exception is the incandescent light bulb with a neodymium coating. The neodymium filters out the yellow and red wavelengths of the visible spectrum leaving predominately blue wavelengths. So even though neodymium light bulbs have a 2800K color temperature, the light they produce appears to be bluer - similar to daylight and to other light bulbs that product light with color temperatures in the 5000K or higher range. When the desired effect is neutral or white, use light sources in the 3000K - 3500K range. For a slightly bluer effect use 4000K. To give the perception of daylight (bluish white light), use light sources with a color temperature of 5000K or higher. It is important to note that color temperature is not the same as color rendering. The color temperature of a light source does not describe or predict the ability of that light source to render color accurately. There are many natural and synthetic compounds that exhibit fluorescence, and they have a number of applications: Lighting The common fluorescent tube relies on fluorescence. Inside the glass tube is a partial vacuum and a small amount of mercury. An electric discharge in the tube causes the mercury atoms to emit light. The emitted light is in the ultraviolet (UV) range and is invisible, and also harmful to living organisms, so the tube is lined with a coating of a fluorescent material, called the phosphor, which absorbs the ultraviolet and re-emits visible light. Fluorescent lighting is very energy efficient compared to incandescent technology, but over-illumination and unnatural spectra can lead to adverse health effects. In the mid 1990s, white light-emitting diodes (LEDs) became available, which work through a similar process. Typically, the actual light-emitting semiconductor produces light in the blue part of the spectrum, which strikes a phosphor compound deposited on the chip; the phosphor fluoresces from the green to red part of the spectrum. The combination of the blue light that goes through the phosphor and the light emitted by the phosphor produce a net effect of apparently white light. Compact fluorescent lighting (CFL) is the same as any typical fluorescent lamp with advantages. It is self-ballasted and used to replace incandescents in most applications. They are highly efficient with high CRI and good color temp index rating. The modern mercury vapor streetlight is said to have been evolved from the fluorescent lamp. The thumbnail below shows the color associated with that kelvin... Hope this info is helpful... Peace!!!
Nice CTRL-C CTRL-V post. I actually know and understand all it says, it may be a bit too technical for most stoners on this forum. Plancks laws? Black body radiation? This may be too large a chunk of techniness for most stoners to swallow. You may want to add a section : what does this mean for my grow? O yeah, 0 K = -273C and not -1273C. RANT : when will you empirial system (ab)users stop horrifying the rest of the world with your system based upon arbitrary values? That system is outright cruel to it's users in it's usefullness, there is no logical relationship between one value and the next. Funny thing is, the US always talk about the 'old' Europe, and how modern they are compared to the rest of the world. Well, we 'old' europeans had some of our geniuses have a look at this mess over 200 years ago and came up with something that makes actual sense: 'the metric system' Going to science class in the US is like going to science class in the dark ages of Europe. No wonder we Europeans are NOT shocked when we learn that only 15% of adults in the US understand technical language as is used in mainstream US newspapers. The other 85% ran away from science class, covering their ears with their hands, yelling 'MOMMY!!!!!'
Fear, you get a for , I give you a for bashing the US and the empirical system? I'm locking this thread and moving your RANT to Pandora's Box.