Normally, light rays from a scene being photographed
pass through the object lens element at the front of the
lens and stay true to the lens’s optical axis.When the lens moves, the beams of light pass through elements
of the lens at the wrong points. More importantly, the image
sensor moves out of position and the light is smeared across the
surface of the sensor, blurring the subject. Preventing vibration
and movement is virtually impossible. Any system that seeks to
reduce blurs caused by camera movement must do something
to put the light beams back on the right path before they hit
the sensor. Electronic image stabilization, which we’ll
look at on the next page, is the
one exception to this rule. It
corrects the blur with soft-
ware after it has
occurred.2
1
Many antishake systems remain dormant until the
photographer has the shutter button partially
depressed. This is so the photographer can move
the camera to frame a shot without having to fight the
camera to position it. When the system is active and
something jostles the camera, the movement is
detected by two gyrosensors, which are gyroscopes
attached to devices that measure motion.
One gyrosensor is positioned to
detect yaw, or horizontal
movement. The other
gyrosensor, mounted
90° away from the
first, reacts to pitch,
or vertical tilting
of the lens.The force from the gyroscope moves the floating plate
toward one or the other of the plates on either side of it.
The change in distance also changes the amount of the
electrical charge on the two outside plates. The charge
increases on the plate that the floating plate moves
close to and decreases on the other plate. The data
the sensors pick up is sent to a high-speed micro-
computer. The microchip measures the charge dif-
ferences and calculates from that the distance
and direction the lens has moved.3
Agyroscopeis basically a highly developed spinning top. The
rapid rotations of its heavy metal disk build up inertiaalong
the same plane that the disk spins. The inertia makes the gyro
resist any force that would change the orientation of its axis.
When this happens, the gyroscope, in effect, pushes back. The
pressure the gyroscope exerts is measured by an accelerometer,
which consists of two metal plates connected to each other and
that sandwich a third plate that floats freely between them.1 2
How Vibration Creates Blurred Images
How Cameras Detect Movement
CHAPTER 8 HOW NEW TECH CHANGES PHOTOGRAPHY^125