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B
ASIC IMAGE PROCESSING
In photography, red, green, and blue are the primary colors. The secondary colors, cyan, magenta,
and yellow, are made from combining the primary colors: cyan = blue + green, magenta = blue + red,
and yellow = red + green. The primary and secondary colors are grouped in complementary pairs:
red and cyan, green and magenta, and blue and yellow.
Knowing the complementary colors is very important in color balancing. If the image has a specific
color cast, either subtracting the color or adding its complementary color will create a natural looking
image.
An introduction to color
Adding or subtracting equal parts of red, green, and blue will have no affect on the color balance.
However, it can change the overall image brightness and contrast. Usually, no more than two color
channels are needed to color balance an image.
Color balancing is a skill that develops with practice. While the human eye is extremely sensitive in
making comparative judgements, it is a poor tool when making absolute measurements of color.
Initially, it can be very difficult to distinguish between blue and cyan, and red and magenta. However,
adjusting the wrong color channel never improves an image; subtracting blue from an image that is
too cyan will give a green cast to the image.
If the image is too
RED
GREEN
BLUE
CYAN
MAGENTA
YELLOW
Decrease the amount of green.
Decrease the amount of blue.
Increase the amount of red.
Increase the amount of green.
Increase the amount of blue.
Decrease the amount of red.
