E. & O. E.
New member
Hi Sanjay,
color temperature is a really nice topic - but IÃ"šÃ‚´m not sure whether iÃ"šÃ‚´t is a topic, which is important for our corals: Sure enough corals will grow under "daylight" (about 6000K) up to 15000K. Obviously they are able to live in a wide "color-range" and thatÃ"šÃ‚´s the reason - I think - why it isnÃ"šÃ‚´t important that the lamp has a cct close to the black body locus.
Nevertheless let me say some words to your last article. You wrote: "we should expect the CCT of metal halide lamps sold in the hobby to be close to black body locus, in the vicinity of their specified color temperature." I wonder, why we should expect this! I think it is as you said: "The aquarium lighting industry has used this color temperature interpretation as a way to label their lamps." And we know, that 15000K is "bluer" than 10000K.
Is it really necessary to use a lamp with cct close to black body locus? I donÃ"šÃ‚´t think so, because even the sun doesnÃ"šÃ‚´t behave like a black body. The Planck-graph for T= 5800 K isnÃ"šÃ‚´t the graph you get from the sunlight.
One reason is that in the highest atmosphere of the sun some elements absorb some lines out of the spectrum and they emitt - send out - them at longer wavelengths. For example hydrogen, magnesium, calcium and natrium. This absorption is the reason for the Frauenhofer-lines. (I mentioned them in my thread "light" same weeks ago.) In our atmosphere oxygen absorbs a line. Ozone absorbs in the uv-area, steam and C02 in the infrared-area. So if you show the photon flux density over the wavelenghts you wonÃ"šÃ‚´t get the distribution of the black body.
Finally the most important thing: Again it was a pleasure to read your "lectures on light"! Your articles remind me of the fact, that our hobby has much to do with physics.
Regards
Erwin Kerkenberg
color temperature is a really nice topic - but IÃ"šÃ‚´m not sure whether iÃ"šÃ‚´t is a topic, which is important for our corals: Sure enough corals will grow under "daylight" (about 6000K) up to 15000K. Obviously they are able to live in a wide "color-range" and thatÃ"šÃ‚´s the reason - I think - why it isnÃ"šÃ‚´t important that the lamp has a cct close to the black body locus.
Nevertheless let me say some words to your last article. You wrote: "we should expect the CCT of metal halide lamps sold in the hobby to be close to black body locus, in the vicinity of their specified color temperature." I wonder, why we should expect this! I think it is as you said: "The aquarium lighting industry has used this color temperature interpretation as a way to label their lamps." And we know, that 15000K is "bluer" than 10000K.
Is it really necessary to use a lamp with cct close to black body locus? I donÃ"šÃ‚´t think so, because even the sun doesnÃ"šÃ‚´t behave like a black body. The Planck-graph for T= 5800 K isnÃ"šÃ‚´t the graph you get from the sunlight.
One reason is that in the highest atmosphere of the sun some elements absorb some lines out of the spectrum and they emitt - send out - them at longer wavelengths. For example hydrogen, magnesium, calcium and natrium. This absorption is the reason for the Frauenhofer-lines. (I mentioned them in my thread "light" same weeks ago.) In our atmosphere oxygen absorbs a line. Ozone absorbs in the uv-area, steam and C02 in the infrared-area. So if you show the photon flux density over the wavelenghts you wonÃ"šÃ‚´t get the distribution of the black body.
Finally the most important thing: Again it was a pleasure to read your "lectures on light"! Your articles remind me of the fact, that our hobby has much to do with physics.
Regards
Erwin Kerkenberg