The camera has never been good, it's useless in low light and the focus is terrible. I've had it since launch, and no updates have rectified this what so ever (and there have been a fair few updates focused on the camera) Samsung forums are full of people saying the same.
Apply gently shock to the phone. If this fixes the issue then you will need a new camera module. Samsung will do this under warranty providing there is no damage (cracks, not scratches and wear and tear)