I have a canon 700d. I have seen other 700d's, and when they focus the lens automatically moves in and out. My one doesn't. Why would that be?
It all depends on which lens is mounted on the camera. If you have an EF-S 18-55mm f/3.5-5.6 IS STM stepping motor lens the front element neither rotates nor moves in and out as it is focusing because it has internal focusing. Many other lenses, such as the EF-S 18-55mm f/3.5-5.6 IS II, do not feature internal focusing and so the front element rotates and moves in and out as focus is changed.