How
sonar
focusing
works
As you beg
in
to
press the shutter
button, your camera releases sound
waves
to
the central part of the scene
(approximate area marked
in
blue).
The frequencies are far beyond our
range of hearing and travel at the
speed of sou nd
(1
,100 feet per
second).
The split second
it
takes for the
sound to reach your subject and
the echo
to
return
is
fed into a tiny
electronic computer inside the
camera.
The computer uses this time mea-
surement to calculate the distance
between the camera lens and your
subject, then signals a motor to turn
the lens until your subject
is
in
sharp focus.
This extraordinary chain of events
takes
place
in less than
113
of a
second.
.
..
echo returns
to
camera .
.....
--
Total
Time
3
4
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