It is important that potential users understand how Canon’s USB implementation affects the FC1. Certain characteristics of Canon’s design make it perform quite differently than a mechanical follow focus, so it is recommended that you read the User Guide and the Canon USB Protocol article.
The Okii FC1 USB Focus Controller gives the photo and video enthusiast a compact yet powerful device that enhances the capabilities of HD video enabled Canon EOS Digital SLR cameras. Like Canon’s EOS Utility, the FC1 uses Canon’s USB protocol to allow control of a wide range of functions, but without the limitations and bulk of being tethered to a computer. The device is handheld, weighing under 5 oz. including batteries, and less than 3" in diameter. It is connected to your camera with a standard mini-B to A USB cable, and can be used as a remote control or attached to a rig using a 1/4"-20 mount located on the back of the anodized aluminum enclosure.
The FC1 uses the autofocus motor in lenses to control focus, even while recording video. This also works in any Live View modes, which can be useful for photography. The HDMI output can still be used in tandem with the controller, so the use of an external monitor is still possible. The nine other switches located around the central focus knob can be used to access important camera functions, such as video start/stop, digital zoom, saving focus points, and adjusting camera settings. The FC1 works great as a remote control for a camera mounted on a crane or jib, giving both setting adjustment as well as focus control from the ground.