Canon Camera Hackers Manual

Contents

232 C H A P T E R 8 Kites, Balloons, and MultikoptersAlternatively, the camera can be controlled from the ground. A verysimple (but sometimes awkward) solution is a thin pair of wires connectedto the USB port of the camera (section 4.9). A more comfortable solution isa radio-controlled (RC) system. One solution is to let the RC system triggerthe camera mechanically (via a servo operating the shutter button). A moreelegant solution is to replace the servo with a device converting the RCsignal into a USB pulse. Devices such as the gentled chdk2 even allow (bymeans of two RC channels) operating up to six configurable camera func-tions (e.g., shutter, zoom, exposure, focus, etc.). Advanced RC systems suchas the DuneCam from Dunehaven Systems can even relay the display imageback to the ground unit, thus giving the photographer some feedback.A more advanced method to mount the camera is a rig that can rotatethe camera vertically and horizontally with the help of servos. Some can evenrotate the camera along its optical axis and can thus change the camera’sorientation from landscape to portrait. The servos are usually controlled viathe 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 anexternal controller such as the Automatic Rig Controller (AuRiCo) that cancontrol 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 usingGyro Servos (again from Dunehaven) instead of normal servos to control therig. Small on-board gyroscopes measure the movements of the rig and ad-vise the servos to counteract those movements.8.2 Balloon-based photographyWhile 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 largeprofessional camera, the balloon, of course, needs to be quite large—andthe helium will be expensive, too. But with a small digital compact camera,the demands on the balloon are minor and balloon photography can bedone at an affordable scale. Even a stack of cheap party balloons could dothe 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 asrigs and RC systems) are the same as for KAP photography.A different category is balloon-based photography in high altitudes, asmentioned in the introduction to this book. In this case, there are additionalrequirements: 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.