Color temperature
White light is commonly describe by it's color temperature. A light source's color temperature is calculated by is comparing it to the color of light a black-body radiator gives off when heated.
Daylight has a color temperature of about 5,500 K. Heating an iron to 5,500 degrees Kelvin emits the same color white light that the sun gives off at noon. Standard tungsten filament bulb lamps have a color temperature of about 3200 K.
- 1,000 K: Oil Lamp.
- 2,000 K: Tungsten Lamp (ordinary household bulb,) Sunrise and Sunset.
- 3,000 K: Studio Lamps, Photofloods, "Warm White" Fluorescent lamps.
- 4,000 K: Clear Flashbulbs, Blue Photofloods, "Cool White" Fluorescent lamps.
- 5,000 K: Blue Flashbulbs, Electronic Flash, Average Daylight.
- 6,000 K: Bright Midday Sun.
- 7,000 K: Lightly Overcast Sky.
- 8,000 K: Hazy Sky.
- 10,000 K: Heavily Overcast Sky.
White Balance
'Color Temperature' is sometimes used loosely to mean 'White Balance' or 'White Point'. Notice that color temperature has only one degree of freedom, whereas white balance has two (R-Y and B-Y): for example, there is no temperature at which a black-body radiator has a purplish hue.
Film Photography
It is important to match the color sensitivity of your film to the color temperature of your light source. Use tungsten film while photographing indoors with incandescent lamps; the yellow light of the tungsten bulbs will appears as pure white in the prints or slides once the film is processed.
Desktop Publishing
In the desktop publishing industry, it is important to know the your monitor?s color temperature. Color matching software, such as ColorSync will measure your monitor's color temperature and then adjust your monitor?s settings accordingly. This enables on-screen color to more closely match printed color. Common monitor color temperatures are as follows:
5000K (D50), 5500K (D55), 6500K (D65), 7500K (D75) and 9300K.
Designations such as D50 are used to classify color temperatures of light tables and viewing booths. When viewing a color slide at a light table, it is important that the light be balanced properly so the colors are not shifted towards the red or blue.
Video Cameras
Most video cameras can adjust for color temperature by zooming into a white object and setting the white balance (telling the camera "this object is white"); the camera then shows true white as white and adjusts all the other colors accordingly. White-balancing is necessary especially indoors under fluorescent lighting and when moving the camera from one lighting situation to another.
Artistic use of color temperature
Experimentation with color temperature is obvious in many Stanley Kubrick films; for instance in Eyes Wide Shut the light coming in from a window was almost always conspicuously blue, whereas the light from lamps on end tables was fairly orange. Indoor lights typically give off a yellow hue; fluorescent and natural lighting tends to be more blue.
Video camera operators can also white-balance to objects which aren't white, downplaying the color of the object used for white-balancing. For instance, they can bring more warmth into a picture by white-balancing off something light blue, such as faded blue denim; in this way white-balancing can serve in place of a filter or lighting gel when those aren't available.
Cinematographers do not "white balance" in the same way as video camera operators: they can use techniques such as filters, choice of film stock, pre-flashing, and after shooting, color grading (both by exposure at the labs, and also digitally, where digital film processes are used). Cinematographers also work closely with set designers and lighting crews to achieve their desired effects.
Compare with brightness temperature.
