Balloon-Based Photography - Canon Camera Hackers Manual

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C H A P T E R 8 Kites, Balloons, and Multikopters
Alternatively, the camera can be controlled from the ground. A very
simple (but sometimes awkward) solution is a thin pair of wires connected
to the USB port of the camera (section 4.9). A more comfortable solution is
a radio-controlled (RC) system. One solution is to let the RC system trigger
the camera mechanically (via a servo operating the shutter button). A more
elegant solution is to replace the servo with a device converting the RC
signal into a USB pulse. Devices such as the gentled chdk2 even allow (by
means of two RC channels) operating up to six configurable camera func-
tions (e.g., shutter, zoom, exposure, focus, etc.). Advanced RC systems such
as the DuneCam from Dunehaven Systems can even relay the display image
back to the ground unit, thus giving the photographer some feedback.
A more advanced method to mount the camera is a rig that can rotate
the camera vertically and horizontally with the help of servos. Some can even
rotate the camera along its optical axis and can thus change the camera's
orientation from landscape to portrait. The servos are usually controlled via
the RC system but can also be controlled via the camera's serial interface
( blue LED) as provided by the SDM (section 7.6). Another option is using an
external controller such as the Automatic Rig Controller (AuRiCo) that can
control both the rig and a CHDK-enabled camera through the USB port.
Especially when shooting video, the motion of the rig can become an-
noying to the viewer. Most of this motion can be cancelled out by using
Gyro Servos (again from Dunehaven) instead of normal servos to control the
rig. Small on-board gyroscopes measure the movements of the rig and ad-
vise the servos to counteract those movements.
8.2

Balloon-based photography

While KAP is dominated by dedicated amateurs, professional photogra-
phers often turn to balloons as camera platforms. A balloon is not as de-
pendent on the weather and is easier to control. When carrying a large
professional camera, the balloon, of course, needs to be quite large—and
the helium will be expensive, too. But with a small digital compact camera,
the demands on the balloon are minor and balloon photography can be
done at an affordable scale. Even a stack of cheap party balloons could do
the job. Nevertheless, transport and storage of balloons remains a chal-
lenge if you don't want to refill the helium for each mission.
Except for the balloon, all of the other required components (such as
rigs and RC systems) are the same as for KAP photography.
A different category is balloon-based photography in high altitudes, as
mentioned in the introduction to this book. In this case, there are additional
requirements: the equipment must be protected against cold temperatures,
and you must provide a way to safely retrieve the camera, such as a para-
chute and a tracking device.