Logitech Quickcam Pro 9000
The Logitech QuickCam Pro 9000 is an expensive and fairly high-quality webcam that is available in several versions. It is of course and UVC device and as such works out-of-the-box in most cases, but if you want to maximize the usefulness of this device on Arch Linux you'll need to do some magic.
I use the webcam to record videos for a blog, and I want the highest possible image quality. As such, I will be capturing uncompressed, raw video and audio, use the autofocus feature of the camera and maintain a constant 25 FPS framerate. Using uncompressed video means you will avoid compression artifacts, minimize CPU load during capture and allows the video encoder to work as efficent as possible when doing the final encoding of the result. By using autofocus (as opposed to having a fixed, inifinite focus) you'll get the sharpest possible image.
By default the camera is limited to 15 FPS as long as auto-exposure is being used. This is because the time required for each frame is longer if lighting conditions are dim as less light hits the sensor. 15 FPS is the hard limit that the autoexposure mechanism must maintain at all times. Unfortunately for us 15 FPS looks really bad, so we need to switch autoexposure off and instead provide good, fixed lighting conditions.
If you just want to use the camera as webcam, you should instead use a compressed format such as MJPEG which minimizes the load on the USB bus and the host CPU. Cheaper webcams typically lacks these compressed formats because they require more hardware and license fees.
By far the best capture software I've found is guvcview. Not only does it allow you to specify exactly the formats to use for both audio, video and container but it also has the ability to control the focus of the camera. Focus control is not part of the UVC standard, and without a software component that handles it you'll not be able to use the AF functionality at all. Unfortunately, guvcview is not available from the regular Arch Linux repositories and has to be built "manually" along with some support libraries.
Building the Software
AUR is the support library needed for AF control. AUR is the viewer/capture application.
Both applications are built easily using the AUR/ABS build system. In the case of libwebcam I used the patches and build scripts provided by esteemed member whitelynx.
Registering Camera Controls
During the installation of libwebcam the following line will be added to your /etc/udev/rules.d/80-uvcdynctrl.rules
ACTION=="add", SUBSYSTEM=="video4linux", DRIVERS=="uvcvideo", RUN+="/lib/udev/uvcdynctrl"
After the installation, disconnect and reconnect your camera to trigger the rules, then start guvcview once as root, just to let it initialize the AF controls. If you are not yet a member of the "video" group, you should add yourself to it and login anew. After this you should be able to use the cameras full feature set, including autofocus, even as a regular user.