Exclamation rear of camera galaxy s4

Good morning and happy Sunday to all,
after the upgrade via OTA to version 4.4.2 kitkat galaxy s4 rear of the camera no longer works, or has worked better in a month 3 times. I state that I have performed a hard reset before and after upgrading. I tried to install (uninstall ĄThen) also third-party applications to see if it worked in this case but nulla.Ho tried to clear the cache but nothing. On the rare times that worked I noticed that opened handling the camera, but the screen remained black, if I tried to activate the front camera and it worked if I tried to reactivate the rear sometimes worked but all with a lag to be frightening. I do not think it is a hardware problem but software. The'm trying them all but I can not get it to work; another proof that I have done is to use the qrcode reader but nothing works even with quell'app.
I thank those who can give me a hand.
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greetings to all