Minolta IIIF - Page 27

Photographic Color Temperature
The Color Meter UE determines the photographic color temperature according to the ratio between
the intensity of light in the blue region and that in the red region of the spectrum; the resulting value
is referred to as ‘‘photographic color temperature”, since it is determined based on the characteristics
of color film. Higher B/R ratios result in higher photographic color temperatures. However, this method
assumes that the spectral power distribution of the light source is continuous with no sharp peaks, such
as those of sunlight and many tungsten lamps.
Although the Color Meter IHF can provide color-temperature readings for light sources with spectral
power distributions which are not continuous or which contain sharp peaks (such as those of fluorescent
lamps), such readings will not necessarily be accurate and may not provide an accurate indication
of how photographic film will respond to such sources. Thus, color-temperature measurements of
such sources are not recommended.
* “Photographic color temperature” is different than the “color temperature’ used in physics and
colorimetry. Basically, color temperature as used in physics and colorimetry refers to the temperature
at which an ideal blackbody would emit light of the same color (having the same chromaticity) as
that of the light being measured.
Spectral power distributions
Kä
400! 100 !-
50! 50+
anes
400 500 600 700 (nm)
i> ch L £
400 500 600 700 (nm)
Sunlight Fluorescent lamp
25