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LIGHT AND IMAGING
LIGHT AND THE HUMAN EYE
Visible light as perceived by the human eye is comprised by a narrow band of electromagnetic energy in the
400-700 nanometer wavelength range, being bounded below 400nm by ultraviolet and above 700nm by infrared.
This visible light region is composed of a spectrum of colors roughly delineated as follows:
Vi o l et 400-430 n m G reen 490 - 560 n m O range 590 - 630 n m
Blue 430 - 49 0 n m Ye l l ow 560-59 0 n m Red 630 -70 0 n m
Because of adaptive properties of the human brain, all light containing some primary components of blue, green
and red energy will generally be perceived as "white light".
The Spectral Energy Distribution Curve (SED) is a graphic representation of a color. The area under the curve
is transmitted. The color shown combines blue-violet components with orange-red.
LIGHT, FILM EMULSIONS AND ELECTRONIC IMAGING SYSTEMS
Unlike the human eye, color film emulsions are designed to record a specific type of light as white
light. Accordingly, emulsions are usually designated as either "tungsten balanced" or "daylight balanced".
When exposing a film emulsion to a light source for which it is not designed, lens filters or
printing filters are usually employed to adjust the color balance of the emulsion to match the color
properties of the particular source.
In video and digital photography, the white balance feature often replaces a lens filter by permitting
some electronic adjustment of the camera’s color sensitivity to the color properties of a particular
light source.
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