Physical temperature and lighting equipment
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Disco Robo
Well-known member
Ha.....Bulb humor is hilarious, but that's Color Temperature not physical temperature.
vidled
DVXuser Sponsor
The short answers are:
- Tungsten/halogen/incandescent lighting equipment can handle low ambient temperatures well.
- Some CFLs/fluorescent lights don't particularly like to be cold when starting them, so those might have to be kept warm before turning them on, or will take a little bit to get to their full output while warming up.
- Tungsten/halogen/incandescent lighting equipment can handle low ambient temperatures well.
- Some CFLs/fluorescent lights don't particularly like to be cold when starting them, so those might have to be kept warm before turning them on, or will take a little bit to get to their full output while warming up.
Centigrade (aka Celsius) and Kelvin degrees are of same size, just that Kelvin scale starts from the absolute zero and Centigrade from the melting point of ice (or freezing point of water if you wish). As the absolute zero is -273.15 C it follows that melting/freezing point of water is 273.15K. All calculations in physics are done in Kelvins (Boyle's law etc).
What is the connection with color temperature? Color tempereature is defined as the tempereature of a black object heated to X degrees Kelvin. A tungsten light filament with 3200K color is basically heated to 3200K which is 3200-273=2927 degrees Centigrade. The surface temperature of the sun is 6000K or 5727C (approx.) and so on.
So, mild frost like -20C/-5F really does not make any difference to the bulb, as the temperature range it has to suffer gets less than 1% bigger (253K to 3200K instead of 273K to 3200K for 0C or 32F)
What is the connection with color temperature? Color tempereature is defined as the tempereature of a black object heated to X degrees Kelvin. A tungsten light filament with 3200K color is basically heated to 3200K which is 3200-273=2927 degrees Centigrade. The surface temperature of the sun is 6000K or 5727C (approx.) and so on.
So, mild frost like -20C/-5F really does not make any difference to the bulb, as the temperature range it has to suffer gets less than 1% bigger (253K to 3200K instead of 273K to 3200K for 0C or 32F)
smelni
Veteran
thats all not true - the color temperature is not the physical temp of the bulb at all. If it were the entire housing would melt - in addition what abou 3200K kinos - you can touch them.
You wrote
"Color tempereature is defined as the tempereature of a black object heated to X degrees Kelvin."
actually it is
"Color tempereature is defined as the COLOR of a PERFECT BLACK BODY
OBJECT heated to X degrees Kelvin."
SO the bulb color temp is 3200K but its physical temp is far FAR FAR lower and not at all related to the color temp
see the wiki def
"
Visible light is commonly described by its color temperature. A traditional incandescent light source's color temperature is determined by comparing its hue with a theoretical, heated black-body radiator. The lamp's color temperature is the temperature in kelvins at which the heated black-body radiator matches the hue of the lamp, and is directly related to Planck's law of black body radiation."
You wrote
"Color tempereature is defined as the tempereature of a black object heated to X degrees Kelvin."
actually it is
"Color tempereature is defined as the COLOR of a PERFECT BLACK BODY
OBJECT heated to X degrees Kelvin."
SO the bulb color temp is 3200K but its physical temp is far FAR FAR lower and not at all related to the color temp
see the wiki def
"
Visible light is commonly described by its color temperature. A traditional incandescent light source's color temperature is determined by comparing its hue with a theoretical, heated black-body radiator. The lamp's color temperature is the temperature in kelvins at which the heated black-body radiator matches the hue of the lamp, and is directly related to Planck's law of black body radiation."
To be precise color temperature relates only to incandesent lights, where the light is made with heated filament (houshold bulbs, tungsten, stars). It is only the filament in tungsten (halogen) lights which is hot (3200K?), not the whole lamp, which surely would melt. Bacause halogen lights run hotter than houshold bulbs the "glass" is actually quatz, not glass which would melt.
Fluorescent lights and LEDs are another matter altogether. There the physical temperature has no relation to the color tempereature, which these lights actually do not have. Only a relative/corresponding color temperature (my english fails here). That means they can imitate black body radiation well enough to be used for photo/video. And run cool.
Yes, my choice of words was bad, your capitalized explanation about color temperature is correct and that's what I was after.
Fluorescent lights and LEDs are another matter altogether. There the physical temperature has no relation to the color tempereature, which these lights actually do not have. Only a relative/corresponding color temperature (my english fails here). That means they can imitate black body radiation well enough to be used for photo/video. And run cool.
Yes, my choice of words was bad, your capitalized explanation about color temperature is correct and that's what I was after.
smelni
Veteran
this is not true - it is not related to the heat of the filament at all - even though the filament of a incandescent light is similar to a black body in the type of light it radiates - it is not the same phys temperature
Take a perfect black body radiator object - heat it to 3200K - record the visual color of it.
Now create a light that radiates that color - that light, regardless of its physical temperature now has a color temp of 3200K -
from wiki
Note: it should not be construed that the color temperature refers to the thermal temperature of anything other than the black-body radiator.) An incandescent light is very close to being a black-body radiator. However, many other light sources, such as fluorescent lamps, do not emit radiation in the form of a black-body curve, and are assigned what is known as a correlated color temperature (CCT), which is the color temperature of a black body which most closely matches the lamp's perceived color. Because such an approximation is not required for incandescent light, the CCT for an incandescent light is simply its unadjusted kelvin value, derived from the comparison to a heated black-body radiator.
Take a perfect black body radiator object - heat it to 3200K - record the visual color of it.
Now create a light that radiates that color - that light, regardless of its physical temperature now has a color temp of 3200K -
from wiki
Note: it should not be construed that the color temperature refers to the thermal temperature of anything other than the black-body radiator.) An incandescent light is very close to being a black-body radiator. However, many other light sources, such as fluorescent lamps, do not emit radiation in the form of a black-body curve, and are assigned what is known as a correlated color temperature (CCT), which is the color temperature of a black body which most closely matches the lamp's perceived color. Because such an approximation is not required for incandescent light, the CCT for an incandescent light is simply its unadjusted kelvin value, derived from the comparison to a heated black-body radiator.
HorseFilms
Look ma no hands
I guarantee you that my 1k burns hotter than my 200w, yet they're both 3200K.
Have you measured the filament tempereature of both, HorseFilms?
A snippet from "smelni": "An incandescent light is very close to being a black-body radiator".
So: what is the temperature of a halogen filament giving 3200K light? Not 2927C, smelni?
And by the way, melting point of tunsten is 3695K, thus it is possible to heat a tungsten filament to 3200K without melting.
A snippet from "smelni": "An incandescent light is very close to being a black-body radiator".
So: what is the temperature of a halogen filament giving 3200K light? Not 2927C, smelni?
And by the way, melting point of tunsten is 3695K, thus it is possible to heat a tungsten filament to 3200K without melting.
Last edited:
Ming
Well-known member
Has ANYONE measured the temperature of the surface of the sun lately? j/k heh.
I am interested whether or not a bulb's (incandesent of course!) color temperature equates to the filament temperature. Common sense says no freakin way a filament is over 2k K under any circumstances. That's really really hot. Then again I'm not the sharpest tool in the shed. Maybe I'll look it up. Or I could do my job. Hmm.
I am interested whether or not a bulb's (incandesent of course!) color temperature equates to the filament temperature. Common sense says no freakin way a filament is over 2k K under any circumstances. That's really really hot. Then again I'm not the sharpest tool in the shed. Maybe I'll look it up. Or I could do my job. Hmm.
vidled
DVXuser Sponsor
Ming said:
Your typical tungsten filament in a houshold incandescent light will be about 2000°K (low wattage) to 2800°K (higher wattage). Like Petrus stated, using slightly different techniques (Halogen) you can get slightly higher temps of the filament, and therefore the color temp too.