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1132 Chapter 15: Lights and Cameras
A. Direct light
B. Reflected light
C. R esu lting amb ie nt light
Color and Lig ht
The color of light depends partly on the process
that generates the light. For example, a tungsten
lamp casts orange-yellow light, a mercur y vapor
lamp casts cold blue-white light, and sunlight is
yellow-white. Light color also depends on the
medium the light passes through. For example,
clouds in the atmosphere tint daylight blue, and
stained g lass can tint light a highly saturated color.
Light colors are
additive colors; the primary light
colors are red, green, and blue (RGB). As multiple
colored lights mix together, the total light in the
scene gets lighter and eventual ly turns white.
Additive mixing of colored lights
Color Temperature
Color temperature describes a color in terms of
degrees Kelvin (K). This is useful for describing
the color of light sources and other color values
that are close to white. The following table shows
color temperatures for some common types of
light, with the equivalent hue number (from the
HSV color description).
If you use these hue numbers for lights in a
scene, set the value to full (255) and t hen adjust
the saturation to meet the needs of your scene.
Mentally we tend to correct light color so that
objects appear to be lit by white light; usually the
effect of color temperature in a scene should be
subtle.
Light s ource Color
Temperature
Hue
Overcast daylight
6000 K
130
Noontime sunlight
5000 K
58
White fluorescent
4000 K
27
Tungsten/halogen lamp
3300 K
20
Incandescent lamp (100 to 200
W)
2900 K
16
Incandescent lamp (25 W)
2500 K
12