Illustration: Knowing Parts of Main A Lens

A lens that we see on the outside will be composed of a main section that looks like this:

 Pictured above is an illustration for the Canon 24-70mm L series, and you have a lens that may have different parts, but at its core a lens have similar functions and names.

Of some of these parts, if we examine further:

1. The front element is the front of the lens optics.
2. Aperture / diaphragm is wide or narrow blades follow our aperture setting. Read more about the meaning of the aperture in the lens
3. Marking is a notation marker lens, you can read more about the naming notation for Canon lenses, Nikon lenses and third party lenses like Sigma / Tamron / Tokina. 
4. Focusing ring is rotated to move the focus point when we use manual focus
5. Auto / Manual Focus mode switch is used to change the focus directly on the lens. The mechanism can be different from one lens to another lens. 
6. Zoom ring is used to change the focal length on a zoom lens
7.  Depth of field scale / distance useful when we use the hyperfocal distance or manual focus
8.  The zoom range is the range of focal length lenses