There will be times, when you want to focus manually rather than letting the camera’s AF system do the job for you. Make sure to change the settings back to AF mode (on the camera as well as on the lens) after you finish shooting with manual focus. It’s even better, if you check all the settings before you start shooting, but there could be times, when you don’t have time for that, right?. You just want to start clicking and you realize that the pictures are out of focus. By the time you realize what’s going on (your camera and lens are still in manual mode), you lose some precious time and moments. It happened to me. Don’t let that happen to you. “You learn from my mistakes”.