Unit of measurement for color temperature of light. Tungsten lamps produce 3,200 K, HMI fixtures 5,600 K, LED panels adjustable between 2,700–6,500 K.
Technical Details
Tungsten incandescent lamps produce 3,200 K, HMI lights 5,600 K, corresponding to midday daylight. LED panels offer variable color temperatures between 2,700 K and 6,500 K with a Color Rendering Index (CRI) of at least 95. Candlelight measures 1,900 K, sunrise 2,000 K, overcast sky 6,000-7,000 K, open shade up to 10,000 K. Modern cameras operate with configurable white balance presets: Tungsten (3,200 K), Daylight (5,600 K), and custom settings between 2,000-10,000 K in 100 K increments.
History & Development
Lord Kelvin developed the absolute temperature scale in 1848 based on gas laws. The film industry adopted the Kelvin system in the 1930s for standardizing artificial light and film emulsions. Kodak introduced the first daylight-balanced films in 1935, followed by tungsten-balanced emulsions for 3,200 K. With the digital revolution since 2000, cameras enable flexible white balancing in post-production, while LED technology from 2010 onwards realizes continuously variable color temperatures on set.
Practical Application in Film
Ridley Scott used mixed light temperatures in "Blade Runner" (1982) – warm 2,700 K neon tubes against cool 5,600 K HMIs for a dystopian mood. Roger Deakins balanced 3,200 K candlelight with 5,600 K daylight in "1917" (2019) using color gels (CTO/CTB). DoPs use color temperature meters like the Sekonic C-800 for precise measurements. Mixed lighting setups require color conversion through orange (85, 1/4 CTO) or blue filters (80A, CTB). LED panels like the ARRI SkyPanel allow live adjustment between 2,700-10,000 K without filter changes.
Comparison & Alternatives
Kelvin differs from the Mired system (Micro Reciprocal Degrees), which represents color temperature differences linearly. One Mired equals 1,000,000 divided by the Kelvin value. RGB systems in LEDs simulate Kelvin values through mixing ratios of red, green, and blue diodes, but rarely achieve the spectral purity of true blackbody radiators. Plasma lighting offers continuous spectra like incandescent lamps but remains costly. Modern workflow programs like DaVinci Resolve digitally correct color temperature deviations but have limited ability to balance mixed light sources within the same frame.