Decamired

Overview

Decamired is a unit of measurement for color temperature and, at the same time, the name of a practical calculation system for color conversion filters. The starting point is the Mired value (English micro reciprocal degree): Instead of calculating directly with color temperature in Kelvin, its reciprocal value is used and multiplied by one million. One Decamired equals ten Mired.

The advantage over pure Kelvin specification: The Mired/Decamired scale maps perceptible color differences more uniformly than the Kelvin scale. An equal Mired step produces a similarly strong visible shift in both warm and cool ranges, while equal Kelvin steps have different effects. This allows filter strengths to be easily added.

Calculation

The Mired value is calculated using the following formula:

• Mired = 1,000,000 / Color Temperature in Kelvin
• Decamired = Mired / 10

For filter determination, subtract the Mired value of the existing light source from the target value (e.g., that of the recording material or the desired color temperature). If the difference is positive, a reddish (warming) filter is needed; if it is negative, a bluish (cooling) one. For example, switching from 5000 K daylight material to 3200 K artificial light requires a shift of around +113 Mired, i.e., a warming filter.

Decamired Filters on Set

Color conversion filters, known as Decamired (e.g., from Tiffen), are based on this logic. They are available in two series: a red series (R, warming) and a blue series (B, cooling). The individual strengths are named after their Decamired value and typically come in densities of 1.5 / 3 / 6 / 12.

• The values are additive: Two R3 filters together produce the effect of an R6.
• Opposite filters cancel each other out: An R6 plus a B6 result in neutral gray.
• By combining red and blue strengths, almost any required correction can be assembled.

Glass filters of this series are available in common studio and matte box formats (e.g., 2x2", 3x3", 4x4", 5.65x5.65", 6.6x6.6", as well as Series 9 round mounts). Unlike universal CTB/CTO gels, the Decamired system allows for fine-grained, computationally traceable adjustment of mixed or unusual light colors.