What is ef?

Some articles on ef:

EF - Other
... Canon EF lens mount, Canon's auto-focus lens mount Eurofurence, a European furry convention ...
Canon EF 100-300mm Lens
... The EF 100-300mm refers to three telephoto zoom lenses produced by Canon ... They are of the EF lens mount that is compatible with the EOS line of cameras ...
List Of 2008 Minnesota Tornadoes
... The 43 tornadoes combined to cause $42.7 million in damage $40.06 million in property damage and $2.66 million in crop damage ... The tornadoes combined to injure 24 people, with one fatality reported from an EF3 tornado in Hugo on May 25 ...