Solution 1: Fix the camera application
Opens the general settings of your Android (slide down the top bar on the screen and tap on the figure of a gear). Then, choose Applications Manager> All> House and there touches on the "Force Stop" button. It also touches on the "Clear Cache" button and "Clear data". Reboot your phone and check if the camera is fixed.
Solution 2: Clear the cache partition
Turn off your phone. Once off, then hold the same buttons Volume Up, Power and Home. When the phone vibrates, release the Power button but do not release the other two. You will enter a special mode called Galaxy Samsung "Recovery". There lies the "Wipe Cache Partition" option with the volume down button, select this option with the power button.
Solution 3: Go to Safe Mode
Turn off the Samsung Galaxy and switch on normally: During the ignition process hold down the volume down button until the phone starts in Safe Mode (at the bottom of the screen the words "Safe Mode" should appear). In this mode only factory applications are loaded device and user applications are disabled: if the camera does work well in this way means that any application that you installed is the problem. Uninstall all applications that think they are causing problems.
Solution 4: Install an alternative camera application
It is possible that the camera application you are using is faulty. Download from the Play Store another camera app as Google Camera or any other that has good grades.
Solution 5: Reset the factory settings
Unlike the first four options, this solution will leave your device as new and will erase everything you've saved or set to it. Be careful to make a backup or backup of your phone. Done that, go to the settings of your Android, option "Backup and Restore" and there choose "Reset factory settings".
If the camera module is damaged
If none of the above works, then surely it is a failure on the part or camera module. Here it is more practical to take your phone to a technical service to replace this piece.