The Color Temperature of Light

Color temperature is a term used to describe the color of light. Every light source has a color temperature. However, color temperature refers to the color value of the light rather than its heat value. Light’s color temperature is measured in units called Kelvin (K). This temperature scale measures the relative intensity of red to blue light.
Warmer light—light that tends to cast an orangish-red tint across the image—has a lower temperature. Neutral or balanced light occupies the midranges, and has no effect on the image’s color values because of its white qualities. Cooler light—light that is blue in appearance—has a higher temperature.

With the invention of color film came a whole new set of considerations. In addition to correctly exposing the image, photographers had to take into account the various color tints different light sources cast across their film emulsion. Film manufacturers improved the situation by developing film emulsions rated for daylight and tungsten lamp color temperature ranges. Camera manufacturers also jumped in and developed color filters, attached to the camera’s lens, to help photographers shoot outside the temperature range of the film. However, these solutions didn’t completely eliminate the problem because images shot in unforeseen and adverse lighting conditions remained irreparable during the printing stage.

[Sources of Light : Prior to the invention of electric lights, electromagnetic energy originated from only a few sources. Even today, the sun is the primary source of light. Fire and candlelight provided evening light for thousands of years, though considerably weaker than modern electric lights. Newer sources of light include incandescent light bulbs, fluorescent light tubes, cathode-ray tubes (CRTs), liquid crystal displays (LCDs), lightemitting diodes (LEDs), and some phosphorescent materials. These light sources directly influence the images you create as a photographer.]