| CaF2 | A synthetic calcium flourite crystal. CaF2 elements provide an excellent correction potential and are about two times more effective than standard UD glass (Ultra-low Dispersion) but it's also far more expensive and only used in few lenses. |
| 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. |
| UD | Ultralow Dispersion glass. A digit after the 'UD' abbreviation means a number of UD glasses in the lens. |
| USM | UltraSonic Motor |
| L | These lenses use special optical technologies [such as] Ultra-low Dispersion UD glass, Super Low Dispersion glass, Fluorite elements, and Aspherical elements |
| EF | Electro-Focus. EF-series lenses for Canon EOS series. Bayonet mount with three outer lugs. |