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I suggest that you first of all try to clear data for camera under settings > apps > all > camera > clear data.
Restart your phone and try again.
if the behavior still persists, I would suggest that you try to boot your phone into safe mode to see if the problem may be related to any 3rd party app that you have installed in your phone:
http://talk.sonymobile.com/t5/FAQ/How-to-boot-your-phone-into-safe-mode/m-p/348008#U348008
