For all you photography newbies out there, I thought id take a minute and go through all the different parts and features of a Canon Camera Lens and their features. and There are Many parts to a camera lens. The picture below has each part of a camera lens described and labeled. I will take a minute to go through each one with you.
The Lens Mount
This is what connects the lens to the camera base, enabling the the camera to communicate with the lens. Not every camera lens can be connected to any camera base. It is a general rule to stick with the same brand as the camera base you have. So if you have a canon camera, you would buy a Canon Lens.
This switch enables you to select either auto-focus (AF) or manual focus (MF) mode. Some Canon Camera Lenses even have additional options.
This enables you to adjust the focal length length of your lens by rotating the ring on the lens barrel which moves the optical elements closer or further apart.
This enables to to manually focus the lens. Most Canon Lenses have automatic focusing but there is an option to override the automatic focus in some situations.
Most Canon lenses have a thread of a specific diameter at the end of the lens barrel that enables you to attach different filters.
Almost all Canon lenses are supplied with a “lens hood” to keep peripheral light from getting to the front of the lens, which is something called flare (not something you want)
The higher end canon lenses have a feature to switch from optical image stabilization modes. Most have two modes, one for general camera shake and one to correct only vertical shake when panning.
This feature is positioned close to the lens mount, and allows you to set aperture manually on the lens rather than the camera.
This feature allows you to calculate depth of field and it helps make use of something called hyper focal focusing. It allows you to maximize front to back sharpness.
I have just gone through all the basic parts and features of a Canon Camera lens, but there is a lot more complexities and a real science to Camera Lenses. If you want to learn more about the technology and science that goes into manufacturing a Canon Camera you should check out Canons Camera Museum web site for a nice graphic illustration of DO technology.