By the time the light emitted from a luminaire reaches our eyes, it has undergone a certain degree of
color mixing
- subtractive, additive or a combination of both .
Subtractive color mixing can be accomplished in two ways. One is when transparent media like color filters are used and the light is only partially transmitted and the other when the light is selectively reflected by colored surfaces.
Three color filters of the
secondary colors
overlapping
one another, creating the
primary colors
and black
in the center.
A red filter on a luminaire will subtract from
white light
(by absorption) all the wavelengths which are not in
the red range.
Most of the
white light
striking a green surface is absorbed.
Only those wavelengths reflected by green pigments are
reflected and seen
Each jellybean reflects a different range of wavelengths.
Lighting designers use both kinds of subtraction.
This table demonstrates the effect of primary
and secondary colored light on surfaces of different colors.
Following are a few examples of the effect of subtractive
color mixing
on the stage:
Here, orange light, strikes a yellow cyc and is reflected as orange. When red light strikes the same yellow cyc, it will cause the cyc to appear red, as orange is in part made up of red.
The yellow ball is lit with
white light
from the right, showing its real color. The red light from the left causes only the red wavelengths to be reflected from the yellow surface, so that on that side the ball appears red.
The blue ball is lit with
white light
from the right, showing its real color. The blue reflects no waves at all from the magenta light on the left so that on that side the ball is totally dark.
Additive color mixing is accomplished by mixing separate beams of colored light . A
beam
combined of two different color beams will appear of a third color.
White
light can be created by adding the three primary colors: red (wavelength 650 nm) which has an orange-red appearance, green (wavelength 530 nm) and blue (wavelength 425 nm) which has a blue-violet appearance
Orfeo, The New Israeli Opera.
The
primary colors
can be mixed in varying proportions, creating a wide range of colors. However,
primary colors
cannot be created by additive mixing of any other colors. In other words, the color red is characterized by a certain wavelength, whereas yellow, for example, although characterized by a
wavelength
of 580 nm, can also be created by additive mixing of two beams of light - red and green.
Colors which are created by the combination of two
primary colors
are called secondary colors. Secondary colors are lighter than primary colors, i.e. of higher energy, as they are comprised of a greater range of wavelengths - at least as many as the sum of the two
primary colors
of which they are formed.
White light can also be created by adding a primary color to a secondary color, for instance a
beam
of blue light added to a
beam
of yellow or a
beam
of red light added to a
beam
of cyan light.
Each primary color is the complementary of a secondary color, making up three pairs of complementary colors. The combination of a pair of
complementary colors
creates white light.
Additive Colors (Mixtures of Light)
Black + Red = Red
Black + Green = Green
Black + Blue = Blue
Black + Red + Green = Yellow
Black + Red + Blue = Magenta
Black + Blue + Green = Cyan
Black + Red + Green + Blue = White
Subtractive Colors (Mixtures of Pigments)
White - Red = Cyan
White - Green = Magenta
White - Blue = Yellow
White - Red - Green = Blue
White - Red - Blue = Green
White - Blue - Green = Red
