SLR camera lens Cha Cha's ring is how the matter
It is in focus, no problem.
2. If the lens has an anti-shake function and is turned on. Canon lens image stabilization is IS image stabilization, Nikon is VR anti-shake. As long as the start of the anti-shake, half-press the shutter when the sound will appear sasa, which is inside the anti-shake at work (is to capture the shock).
There may be two sounds in the lens.
1. If the camera has a real-time focus function, Nikon called AF-C, is a continuous servo focus. Then if the lens detects the focus to the object of the distance changes, it will focus back and forth, part of the lens on the zoom more hesitated, there will be focus on the situation. So it will sound.
