Share your experience!
Clear data for camera under settings > apps > all > camera > clear data. Turn off the phone, remove the SD card from the phone. Start the phone again and try to access the camera.
still not work 
In that case I suggest that your repair the phone software using PC Companion:
http://www.sonymobile.com/update
In PC Companion, press start on Support Zone > Start on Update the phones software > "Repair phone".
If the problem still persists you should have the phone examined by a service center. For more information, please contact your local Xperia support team: