kennedymax
Well-known member
Is this the center line (average) of the daylight and tungsten spectrums, or what?
Why is daylight measured as 5600K and tungsten at 3200k?
- Thread starter kennedymax
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David G. Smith
Steak Knife Member
David G. Smith
Steak Knife Member
maranfilms
Veteran
Yup, or simply put, it's based on a kelvin chart. Different light has different temperature. it's that simple. daylight is 5,200-5,500 or so. then subtract from that, the color temp goes down so does the blue spectrum, thats why tungston halogen is 2,800-3,200. and is more yellow. so to correct that and make it daylight temp, you need to add ctb (color temp blue, 1/4, 1/2 , full.) gel to your light. or reverse it, and add cto( color temp orange) to daylight rated lamps. But keep in mind, every time you add gels to your lights, you lose light, and therefore need to compensate for the loss.
Take Davids advice and spend some time reading the links he provided, there's a lot more to it then my simple explanation.
Take Davids advice and spend some time reading the links he provided, there's a lot more to it then my simple explanation.
David G. Smith
Steak Knife Member
The one thing to remember, if you are just learning the basics is that the "Temperature" part is based on the temperature (In degrees Kelvin) that a theoretical black body would need to be heated up to to emit light at the color (Or spectrum wave length) specified. What always helps me is just visualizing the spectrum of visible light from infra-red to the left (Lower degrees K) to Ultraviolet (Higher degrees K) to the right.
Gabel
Well-known member
And when shooting on film, you would also use a filter on the camera! It's much more common in both cases to use orange filters than blue ones. A full CTB, taking a tungsten lamp to 5600K will take away 3/4s of it's output, making a 2K output as much as a 500 watt light... The best example is on film. An 85 filter, an orange filter to use tungsten film in daylight (which is very common) takes away 2/3rds of a stop, which is an OK loss (and in daylight, one can live with a bit of light loss) while a blue filter an 80, which turns daylight to tungsten takes away 2 full stops. Considering tungsten is mostly used in doors, where light levels are lower, this is very problematic and rather uncommon.
Moseph
Veteran
In practice, many will say that CTB it's a 2 stop reduction, but in reality it's closer to 1 and 2/3 of a stop. Which can still be, as you stated, problematic to say the least.
David W. Jones
Veteran
Makes more sense to just switch to a daylight film stock for shooting daylight, and a tungsten film stock for shooting under tungsten lamps.
Of course all that will likely be a moot point by the end of next year.
Of course all that will likely be a moot point by the end of next year.
tommygdawg
Well-known member
Wouldn't there still be an issue when mixing daylight with tungsten lamps?
sonofaresiii
Well-known member
I think he was talking in response to putting a filter on the camera, which (not that I shot much professionally back when film was big) I understand it was pretty rare... because yeah, you could usually just switch stocks. Any issue fixed by an on-camera color correcting filter could also be fixed by switching stocks.
notharrylume
Active member
To the OP:
On a practical basis light of color temperature X does indeed consist of a spectrum of light, not just one frequency. The sun and other thermal light sources generally emit this full spectrum light, and generally this is what we think of as high quality light. As the others have mentioned that Kelvin number is the heat that theoretical black body geratiing that color lilght.
Non thermal sources, some of which include discharge type lights such as fluorescent, emit light in a discontinuous spectrum with spikes of various frequencies. Calculations are made and these sources are assigned calculated light temperatures, based on some sort of averages. Fluorescents tyoically have a large green spike, which is then balanced with other color spikes to get to an average of "dayllight" (5600k) or "tungsten" or whatever. But because this light consists of the average of spikes we generally find this light less attractive than full spectrum lights.
"CRI" (color rendering index) is a measure of the qualilty of light with 100 representing the ideal full spectrum light of any particular temperature. By adding colored phosphors some manufactures of fluorescents increase the number of frequencies being emitted and thus increase CRI and quality. In general flos of CRI's in the 60's look awful, and those aove 90 begin to look better.
When you add a filter you change all the frequencies generated of the source, so when you filter a tungsten source, you still have the beautifull light of a full spectrum, just raised or lowered by the type of the filter.
On a practical basis light of color temperature X does indeed consist of a spectrum of light, not just one frequency. The sun and other thermal light sources generally emit this full spectrum light, and generally this is what we think of as high quality light. As the others have mentioned that Kelvin number is the heat that theoretical black body geratiing that color lilght.
Non thermal sources, some of which include discharge type lights such as fluorescent, emit light in a discontinuous spectrum with spikes of various frequencies. Calculations are made and these sources are assigned calculated light temperatures, based on some sort of averages. Fluorescents tyoically have a large green spike, which is then balanced with other color spikes to get to an average of "dayllight" (5600k) or "tungsten" or whatever. But because this light consists of the average of spikes we generally find this light less attractive than full spectrum lights.
"CRI" (color rendering index) is a measure of the qualilty of light with 100 representing the ideal full spectrum light of any particular temperature. By adding colored phosphors some manufactures of fluorescents increase the number of frequencies being emitted and thus increase CRI and quality. In general flos of CRI's in the 60's look awful, and those aove 90 begin to look better.
When you add a filter you change all the frequencies generated of the source, so when you filter a tungsten source, you still have the beautifull light of a full spectrum, just raised or lowered by the type of the filter.
Gabel
Well-known member
Sometimes yeah, sometimes not. Different stocks have different feel, dynamic range, speed and so on. Then it makes more sense to order one stock and filtrate it. Standard is to use Tungsten stock, which is still very common (filtrated too, just saw Looper which was shot exclusively on 5219 which is a tungsten stock).
David W. Jones
Veteran
Well I shot film for some 35 years and always had a good supply of both D & T stocks in various speeds stocked in the studio fridge, as well as a complete set of filters. We would tend to do what worked best for the situation. But like I said, it's really a moot point as film goes bye bye.