How Passive Autofocus Sees
Sharp and Fuzzy
Light passing through the lens of a
camera is diverted from the image
sensor at the back of the camera
by a mirror, or prism.1
The light falls on a strip of 100–200
photocells, called linear sensors, which
are similar to those that make up the imag-
ing sensor. The strip is positioned so that
the distance the light travels to it is equal to
the distance to the imaging sensor.2
42 PART 2 HOW DIGITAL CAMERAS CAPTURE IMAGES