| 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. |
| Float | Floating elements are a relatively reliable indication for a good performance towards closer focus distances. |
| 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. |
| IS | Image Stabilizer. Allows the lens to sense movement from "shake" or vibrations, and instantly apply an optical correction by moving a group of lens elements. |
| S-UD | Super Ultra-low Dispersion glass. Is better than UD but still worse than CaF2. |
| 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. |