Washtenaw Community College Don Werthmann The Scale Defines the of Cooler Light Source 13,000 K 12,000 K sky, no direct : 11,000 K to 13,000 K 11,000 K 10,000 K 9,000 K

8,000 K Overcast Sky: 8000 K 7,000 K Average : 6500 K 6,000 K Electronic : 6000 K 5,000 K Noon : 5500 K — DAYLIGHT Film viewing tables, bulbs, HMI 4,000 K Studio Light, Type A: 3400 K 3,000 K Studio Light, Type B: 3200 K — Household Lightbulb: 2800 K 2,000 K Candlelight: 1900 K 1,000 K Warmer Light Source

Kelvin (K) defines a specific property of light that is emitted by a or other astronomical object. A body—known as or 0 K—is a theoretical stellar object that has a surface which absorbs incident radiant but cannot reflect any (light). The scale interprets the to which a would have to be heated for it to emit light of a given color. The Sun at mid- emits a of 5500 K ( light) and is the standard that color photographic materials, image input devices, analog or computer processing equipment, and output devices are manufactured. The illustration above interprets commonly used color of light. Note that ordinary ideas of color—the warmth or coolness of thermal temperature—don't match what you think it to be. Although is known as a warm color, the color temperature of red/warm light is LOW on the Kelvin Scale. Similarly, blue is known as a cool color but its color temperature is HIGH. The illustration below compares the relativity of the Kelvin and scales.

5,500 0 373 3,200 7,500 15,000 30,000 45,000 60,000 Kelvin Black Sun Hottest °Fahrenheit -460 212 9,980 26,540 53,540 80,540 107,540

—Text adapted from Sears and Zemansky’s University , 6th Edition, pg. 323 —Illustration adapted from : From the Earth to the , 2nd Edition, appendix 13