The Tiffen 4 x 5.65" Decamired Blue 3 Cooling Glass Filter - For those who want a foolproof way to obtain accurate colour temperature readings, the decamired system is the solution. Using this formula, you can easily and quickly transpose temperatures from one point to another.

This system is also useful when you want to bring a certain creativity to colour photography.

Applications include maintaining constant colour temperature throughout the day and producing the effect of different times of day. Available in two series, reddish filters that warm the light and bluish filters that cool the light. Each series contains 4 densities: 1.5, 3, 6 and 12. Filters from the same series can be combined.

Decamired filters are designed to handle unusual colour temperature variations more easily than the previously mentioned filters. Available in increments in the red and blue series, decamired filters can be easily combined to create virtually any correction required. By measuring the colour temperature of the light source and comparing it to that for which the film was designed, we can predict the required filtration fairly well.

A filter that produces a colour temperature change of 100K at 3400K will produce a change of 1000K at 10,000K. This is because the filter relates to a visual colour scale. It will always produce the same visible difference. A colour change of 100K at the higher temperature would be barely noticed.

Calculations
To use this concept, subtract the mired value of the light source from that of the film. If the result is positive, you need a reddish filter; if it is negative, use a bluish filter. Filters coordinated in mireds are called decamireds. The mired value divided by ten gives the decamireds. The 60 mired shifts, above, would be produced by an R6 filter, where the higher values were those of the lighting.

Sets of these filters are typically available in values of 1.5, 3, 6 and 12 decamireds in colours B (bluish) and R (reddish). These numbers are additive; that is, a pair of R3 produces an R6. An R6 plus a B6 cancel each other out to produce a neutral grey.

The decamired system has an advantage over the Kelvin system in that the Kelvin scale is not linear

Decamired readings provide more accurate/controllable readings than Kelvin

The difference between the Mired value of the film and the Mired value of the light is the Mired value of the correction filter that correctly matches the light to the film

A simple formula
-Mired Value = 1,000,000 : Kelvin Value
-Kelvin Value = 1,000,000 : Mired Value
-For 5600K daylight colour film, the Mired value is 1,000,000 divided by 5600 = 178.6
-For 3000K tungsten light, the Mired value is 1,000,000 divided by 3000 = 333.3
-178.6 Mired - 333.3 Mired = -54.7 Mired, or -5 Decamired
-A positive value indicates a reddish KR filter, a negative value indicates a bluish KB filter
-Thus, the filter required to match 3000K halogen light (the slightly low value results from the mains voltage being lower than its nominal voltage) to 5600K daylight colour film is a blue conversion filter

ColorCore Technology
-Tiffen filters are manufactured using ColorCore technology, a closely guarded proprietary process that involves permanently laminating the filter material between two pieces of optical glass ground flat to tolerances of one ten-thousandth of an inch, then mounted in precision metal rings
-The ColorCore process allows Tiffen to control the colour and density of their filters, as well as the characteristics of special effects filters with precision far superior to typical mass-tinted filters, which typically exhibit colour and density variations

Superior Quality
-Hollywood's major film studios rely on Tiffen filters for their multi-million pound productions
-The superior quality and design make Tiffen the overwhelming choice of filmmakers, professional photographers and even NASA
-Tiffen has also received an Emmy from the Academy of Television Arts and Sciences for its engineering excellence