Every now and then you fire up PhotoBooth, or FaceTime or another OSX app but it show no camera as being connected!!! Its seriously annoying to have to restart. Luckily there is a fix that doesn't require a restart at all :)
Try this:
First close all camera apps.
1a) Open 'Terminal' application
1b) Type sudo killall VDCAssistant and hit enter
1c) Enter the sudo (your admin) password
1d) Open your camera app
if that doesn't solve it, then you will need to shutdown and then boot-up again (as the restart wont help in that case) but that has only ever happened to me the once.
Hope that helped.
Peace.
