The Textbook of Digital Photography - PhotoCourse

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imAge sensors—it’s All blACk And white AFter All

Because each pixel
on the sensor has a
color filter that only
lets through one color,
a captured image
records the brightness
of the red, green, and
blue pixels separately.
(There are usually twice
as many photosites with
green filters because
the human eye is more
sensitive to that color
so green color accuracy
is more important.)
Illustration courtesy of
Foveon at http://www.foveon.
com.

To create a full
color image, the
camera’s image
processor calculates,
or interpolates, the
actual color of each
pixel by looking at
the brightness of the
colors recorded by it
and others around it.
Here the full-color of
some green pixels are
about to be interpolated
from the colors of the
eight pixels surrounding
them.

Each pixel on an
image sensor has
red, green, and blue
filters intermingled
across the photosites
in patterns designed to
yield sharper images
and truer colors. The
patterns vary but the
most popular is the
Bayer mosaic pattern
shown here.