The typical lens, like the ones shown in Figures 2.13 and 2.14, has seven or eight common features. Not every component appears on every lens. The 18-55mm lens on the left, for example, lacks the distance scale and distance indicator that the 17-85mm lens on the right has. Lenses that lack image stabilization will not have a stabilization switch.
Filter thread. Lenses have a thread on the front for attaching filters and other addons. Some also use this thread for attaching a lens hood (you screw on the filter first, and then attach the hood to the screw thread on the front of the filter).
Lens hood bayonet. This is used to mount the lens hood for lenses that don’t use screw-mount hoods (the majority).
Zoom ring. Turn this ring ...