| USM | UltraSonic Motor |
| FTM | Full Time Manual Focus. This allows the lens to be manually focused without leaving automatic focus mode and without damaging the lens. This works best with cameras that can shift the autofocus from the shutter release to another button. |
| I/R | Inner/Rear focusing ring. Focusing is performed by moving one or more lens groups positioned between the front lens group and the diaphragm. |
| EF | Electro-Focus. EF-series lenses for Canon EOS series. Bayonet mount with three outer lugs. |