Practical Artistry: Light & Exposure for Digital Photographers

126 Using Light

So far, I’ve explained light as something that has an in-

tensity (or strength) that can be measured and defined

using exposure settings. In addition to this quantita-

t

ive view of light, any given light source has a level of

warmth or coolness.

This apparent warmth or coolness of a light source

corresponds to the frequency of the light waves emit-

t

ed by the source, and is measured in degrees Kelvin

(see table). The lower the number of degrees Kelvin,

the redder the light; and the higher the number of de

-

g

rees Kelvin the bluer the light. Any light below about

2000K is very orange or red, light in the 3000K–4000K

range appears yellow, light in the 5000K–6000K range

appears roughly neutral, and any light source above

7000K seems blue.

Below is a table showing the color temperature of light

in degrees Kelvin. The asterisk (*) indicates a pre-set at

that temperature in Adobe Camera Raw.

Another way of describing the scale of Kelvin values

is that light moves from warm in the psychological

perceptual sense (at lower Kelvin values) to cool, again

perceptually (at higher Kelvin values).

In the old analog days, photographers used color film

that was balanced for a particular light source (and

color temperature). This color balance could not be

changed, except by changing the light source itself or

by using a filter on the camera designed ...