Color Temperature
The final consideration in lighting equipment actually is a part of the camera operation, but the problem starts with the source of light. All light sources are not equal in their actual color. The human eye and mind compensate for this variation by creating the illusion that light within a certain range appears white. Actual measurement of the color of light is in degrees Kelvin, based on the color of a carbon heated and measured at certain temperatures. The lower the Kelvin temperature, the more reddish yellow the light appears; the greater the Kelvin temperature, the bluer the light appears.
There is no actual “white light” on the Kelvin scale. Typical candlelight measures less than 1,800 K. An ordinary incandescent light bulb measures 2,800 K. Professional tungsten-halogen lamps measure 3,200 K. Daylight varies from approximately 4,000 K to more than 12,000 K, but the standard is considered 5,400 K. The lower the Kelvin temperature, the “warmer” the color is; the greater the Kelvin temperature, the “cooler” the color is.
The critical factor concerning the color temperature is that a camera sees and reproduces the actual color of the light source as it is reflected from the subjects. An electronic camera can be adjusted to compensate for any variation in the color temperature by the process of white balancing. To light a scene properly, though, it should be lit with consistently color-balanced light sources.
Professional lamps are accurately rated for their color output, but when shooting in the field, you may be in an environment where the light sources are not controlled. Home incandescent lighting is warmer than studio lighting; office fluorescent lighting is bluer and greener than other lighting. (Normal consumer fluorescent lamps do not have a specific Kelvin temperature because they are a pulse light.) If you are shooting next to a window, the daylight entering the window does not match the color temperature of the production lamps. This situation is called mixed lighting.
When arranging lighting, it is necessary to take into consideration the color temperature of the available light sources by measuring them with a Kelvin temperature meter or by arranging to have all light sources be of the same color temperature.
Fluorescent light does not emit a specific color temperature but can be filtered either at the camera or on the tubes themselves to correct the temperature to match the camera settings. Newer fluorescent tubes that have been designed to match 5,400 K are currently available.
| Color Temperature | Light Sources |
| 1,850 K | Open Flame |
| 2,000 K |
Wom household lamp Sunrise, sunset |
| 2,800 K | Unshaded new house hold lamp |
| 3,200 K | Quartz-Halogen studio lamp |
| 3,400 K | Photoflood lamp |
| 4,250 K |
Early morning, late afternoon sunlight |
| 4,800 K | Fluorescent lamp
(that is pulse lamp, and do not emit a specific color temperature, but do emit light with a high blue-green content that may be compensated for with proper filtering) |
| 5,000 K | Carbon arc lamp |
| 5,400 K | Noon sunlight |
| 5,600 K | HMI lamp |
| 6,000 K | Overcast sunlight |
| 8,000 – 20,000 K | Direct blue sunlight |
