B+W 1057404 Datasheet download pdf (Page 18)

KB ¡2

MIRED

Neutralized with Conversion Filter KB 12

Reddish evening light before sunset Moonlight effect with Conversion Filter KB 6

Halogen illumination with daylight lm

B+W Tip: Compute with Mired

Color temperatures in Kelvin must not be

numerically added or subtracted because

they do not behave linearly. Sums or differ-

ences calculated in this manner lead to false

results. With a simple formula, however,

Kelvin values can be converted into Mired

values, which can then be added or sub-

tracted from the Mired values of the filters:

 Mired value = 1000000 : Kelvin value

 Kelvin value = 1000000 : Mired value

For 5600 K daylight color film, the Mired

value is 1000000 : 5600 = ¡78.6.

For 3000 K artificial light, the Mired value is

1000000 : 3000 = 333.3.

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 tailors the light to the film:

¡78.6 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

adapt the 3000 K halogen light (the slightly

low value results from the mains voltage

being lower than its nominal voltage) to a

5600 K daylight color film is a blue KB ¡5

B+W Conversion Filter.

A diagram for Kelvin/Mired conversion, and

for the determining the correct filtration for

photographs can be found on page 65.

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B+W 1057404 Datasheet Page 18