A mired, or micro-reciprocal degree, is a unit used to measure the colour of light. It is calculated by dividing one million by the colour temperature of a light source in kelvins. For example, a 5500K light source has a mired value of 182 (1,000,000 ÷ 5500). This measurement provides a precise way to quantify the warmth or coolness of light in photography.
Understanding mired values is especially useful for photographers when selecting filters to balance film or digital sensors under different lighting conditions. By knowing the mired difference between two light sources, photographers can accurately correct colour casts and achieve consistent, natural-looking images.