Nanometers to Kelvins ?

[Kyle McClain]

Does anyone know how to convert one to other?

Thanks.

KM

[cj7jeep81]

Do you mean which kelvin bulb best match the light at a particular ocean depth? If so, I believe the deeper you go, blue light penetrates best.

[Kyle McClain]

Actually I want conversion from kelvins (color temprature) to nanometers (wavelength). I am doing research on some new bulbs and some of the documentation does not provide both measurements.

Here is an example.

Actinic light is around 7100 kelvins. The wave length for that spectrum of light is about 420 nano meters.

I was hoping that some one know about a conversion formula or a table of conversions.

Thanks anyway.

KM

[theearthling]

There is no such conversion. Kelvins are a measurement of the overall color-temperature of a light source, which includes a wide range of frequencies. If you're pinpointing light at a specific wavelength, you're talking about a monochromatic source (instead of white light, light of a specific color), such as that emitted by an LED.

[Kyle McClain]

LED's don't emitt a single wave length. For example the blue gallium ion LED's peak at 430 nm but emit a broader spectrum of light. This is what I am looking for. Again I will use this example.

Actinic light peaks around 420 nm. Actinic light is around 7100 kelvins.

SO Daylight peaks at XXX nm and is around 6500k.

I want the peak in nanometers at a specific kelvin rating.

[theearthling]

Originally posted by Kyle McClain
LED's don't emitt a single wave length. For example the blue gallium ion LED's peak at 430 nm but emit a broader spectrum of light. This is what I am looking for. Again I will use this example.

Actinic light peaks around 420 nm. Actinic light is around 7100 kelvins.

SO Daylight peaks at XXX nm and is around 6500k.

I want the peak in nanometers at a specific kelvin rating.


True about LEDs, but they have a single peak, and are considered monochromatic light. However there is no such conversion from nm to Kelvins. Lamps rated on the Kelvin scale emit a spectral power distribution that may contain several different peaks, but will often be flat over a wide range of wavelengths. That's why lamps rated in terms of Kelvins appear to be different hues of "white." They are basically emitting light in all colors, at all visible wavelengths, though in different proportions. It is the differences in these proportions that makes one source look more blue (10,000 Kelvins) or more orange/yellow (3200 Kelvins)

Here's a graph comparing several different light sources, which may help answer your question:

Spectral Power Distribution of Sunlight vs Artificial sources (http://www.atlaswsg-japan.com/spd.htm)

However, just because two sources are rated the same color-temperature, does not mean they have the same SPD. Often, this rating, as provided by manufacturers, is only an approximation, and it will change over the life of the lamp.

[baron_vonklyff]

Actually Kelvin is a measurement of heat. The peak kelvin for a bulb is the peak heat of the spectrum that the light is simulating. This peak is the peak of the black body curve for a light source with that Kelvin equivalent temperature. Conversion to nanometers is not possible in the units that you are describing since you cannot directly convert temperature to wavelength. However, with some knowledge of physics and the ability to manipulate formulae given certain other variables it could be done.

Now, to the question of a table....I have not heard of one, but I am sure that someone has come up with something that gives at least a general equivalency. Unfortunately, I don't know where to find something like that. Check with some of the researchers on lighting in the various experts forums. That is where I would go.

[theearthling]

Originally posted by baron_vonklyff
Actually Kelvin is a measurement of heat.

Correct, and the color-temperature scale is defined in terms of the color emitted by a blackbody source at a certain temperature.


The peak kelvin for a bulb is the peak heat of the spectrum that the light is simulating.

There may be no discernable peak in the SPD for a light source. In fact, a truly white source would emit light at equal intensities across all wavelengths.


This peak is the peak of the black body curve for a light source with that Kelvin equivalent temperature. Conversion to nanometers is not possible in the units that you are describing since you cannot directly convert temperature to wavelength. However, with some knowledge of physics and the ability to manipulate formulae given certain other variables it could be done.

Now, to the question of a table....I have not heard of one, but I am sure that someone has come up with something that gives at least a general equivalency. Unfortunately, I don't know where to find something like that. Check with some of the researchers on lighting in the various experts forums. That is where I would go.

There's really no way to come up with a table to convert color-temperature to nm. That's like mixing a number of random colors in a bucket and asking: "Is it red, orange, yellow, green, blue, indigo, or violet?"

[Frick-n-Frags]

Actually Kelvin temp is a rating for molecular motion, which at 0º Kelvin, all molecular motion stops.

There are points along the Kelvin scale where the electromagnetic radiation emitted by the molecular motion could be called "heat", but at other times it is longwave radio or visible light or cosmic rays.

Kelvin temp ratings do only apply to monochromatic light and wider spectrum lamps can only be Kelvinized via an average color, which poorly tells the whole spectra story.

LED's put out very specific frequencies of monochromatic light because each time an electron of the semiconducor material is ionized up an energy band, and then drops back into a lower band, it puts out a very defined freq. photon of light because it is dropping from very defined atomic energy bands of very specific compounds.

I would also say there is a definite relationship between ºK and frequency(or wavelength, whatever) of EM radiation. You just might have to get a bigger scale than just visible light to nail it. I would say get 3 points and infer the linearity from there. (I don't want to get out physics books, that's your job :D, but 0ºK is infinite wavelength so I don't know what the real linearity of the whole scale is, maybe there is a log relationship etc. I just know that 0ºK is some kind of divide by zero to equal infinity length wavelength)