Mired Value

Overview

The Mired value (from English micro reciprocal degrees) is a unit of measurement for describing color temperature. Instead of stating the color temperature in Kelvin (K), the reciprocal is calculated and multiplied by one million. The unit is used in lighting because equal Mired differences over the entire relevant range (approximately 1,000 K to 10,000 K) correspond to approximately equal perceived color differences — unlike the Kelvin scale, where a 200 K difference in the tungsten range (3,200 K) appears optically much stronger than 200 K in the daylight range (5,600 K).

In practice, the Mired value is primarily relevant for gaffers and lighting technicians as the Mired shift value of conversion filters (CTO, CTB). Since Mired shifts are additive, the values of multiple gels can be easily added or subtracted to determine the total correction needed.

Calculation

The conversion is done using a simple formula:

• Mired = 1,000,000 / Color Temperature in Kelvin
• Example: 5,500 K corresponds to approximately 182 Mired (1,000,000 / 5,500).
• Example: 3,200 K corresponds to approximately 312 Mired (1,000,000 / 3,200).

The Mired shift of a filter is the difference between the Mired values of the source and target color temperatures. Since the reciprocal is used, warming (lower Kelvin number) results in a positive shift, and cooling (higher Kelvin number) results in a negative shift.

Use on Set

The Mired shift is used to select the appropriate correction filter to match one light source to another — for example, to "pull" a tungsten spotlight (artificial light) towards daylight or vice versa, to correct daylight through a window to artificial light.

• CTO (Color Temperature Orange) warms the light, thus having a positive Mired shift — typically for correcting daylight or HMI to tungsten.
• CTB (Color Temperature Blue) cools the light, thus having a negative Mired shift — typically for correcting tungsten to daylight.
• Both are available in gradations (Full, 1/2, 1/4, 1/8), whose Mired shifts are proportional and can be added: two 1/4 CTO gels result in the same correction as one 1/2 CTO gel.

The following table shows typical conversions of common Rosco Cinegel filters. The specific Mired shift numbers may vary slightly depending on the manufacturer (Rosco vs. Lee) and data sheet generation, which is why manufacturer data sheets should always be consulted for exact values.

Note: Strictly speaking, the term "Mired" is considered outdated; Kodak and others alternatively use "reciprocal megakelvin" (MK⁻¹ or 1/MK), with numerically identical values.