I had an issue after upgrading to Mavericks where Photo Booth, Facetime, and Skype could not detect my camera, and kept telling me there were no connected cameras.
I found a fix on the Apple discussion forum that works, and I will share for anyone else that might be affected:
- Quit all open apps that may try to use the FaceTime camera
- Open Terminal, found in the /Applications/Utilities directory in OS X
- Enter the following command string exactly, then hit return:
sudo killall VDCAssistant
- Enter the administrator password when requested, this is required to execute a command with superuser privileges as prefixed by sudo
- Relaunch the app that was attempting to use the camera