1. Quit all open apps that may try to use the FaceTime camera
  2. Open Terminal, found in the /Applications/Utilities directory in OS X
  3. Enter the following command strings exactly, then hit return:
sudo killall VDCAssistant

    4. Still at the terminal, issue the following command as well:

sudo killall AppleCameraAssistant

   5. Enter the administrator password when requested, this is required to execute a command with superuser privileges as prefixed by sudo

   6. Relaunch the app that was attempting to use the camera

For more information, please check http://osxdaily.com/2013/12/27/fix-there-is-no-connected-camera-error-mac/ or https://www.youtube.com/watch?v=P-6kTfqn-b8 for a video tutorial. 

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