Kelvin
From The Glossary of Digital Photography
A temperature scale. The unit is the kelvin (not capitalized), while the scale is Kelvin (capitalized). The unit is not degrees kelvin, but simply kelvin, with the symbol K. It is similar to the temperature scale of Celsius, except the zero point of the Kelvin scale is absolute zero, the coldest temperature that is possible. The individual whole-number temperature intervals (called degrees in Celsius, but not in Kelvin) are the same in each scale. Absolute zero is equal to -273.15 0C. The Kelvin scale has no negative numbers because of this definition. In digital photography, the Kelvin scale is used to specify the color temperature of light. The temperature of light at noon on a sunny day is about 5500 K. Ordinary incandescent light bulbs are about 3200 K. The Kelvin scale was named after Lord William Thomson Kelvin, who created it in 1848. See also [[color temperature]]
