Color Temperature Calculator

Color temperature in Kelvin describes how warm or cool a light source looks, but Kelvin itself is a poor unit for choosing correction gel because equal Kelvin differences don't produce equal visual shifts -- the eye and correction filters respond more linearly to Mired, calculated as one million divided by the Kelvin value. This calculator converts your Color Temperature to Mired and compares it against Mired Shift from Daylight, the standard 5600K reference point cinematographers correct toward or away from. Mired moves in the opposite direction from Kelvin across the calculator's full 1000-20000K range: a higher color temperature always produces a lower Mired value, and Mired Shift from Daylight follows the same inverse relationship since it's just Mired offset by a fixed constant. That Mired Shift crosses exactly zero right at 5600K, which is the calculator's dividing line between the two correction families -- CTO (color temperature orange, for warming a cool source down toward tungsten) and CTB (color temperature blue, for cooling a warm source up toward daylight).

CTO Equivalent and CTB Equivalent translate that Mired Shift into a rough percentage of a "full" correction gel, using separate reference points for each direction since gel manufacturers don't rate CTO and CTB symmetrically: a full CTO (warming toward tungsten, in the style of Lee 204) is roughly a 159-Mired shift, while a full CTB (cooling toward daylight, in the style of Lee 201) is roughly 137 Mired. Actual gel ratings vary by manufacturer and specific product, so treat these percentages as a rough guide to gel strength rather than an exact spec for any one brand's filter. The Warm/Cool Index gives a quick -2-to-+2 read on which lighting-temperature zone your source falls into, from tungsten-warm at the low end to shade-cool at the high end, and never moves backward as Kelvin rises across the full range.