If you’re a crop sensor Canon shooter, you may have learned in the past that the ‘S’ in EF-S stands for “Short-Back Focus”. Well, that’s not true anymore. The lens mount was originally for lenses with rear elements closer to the sensor plane than in EF lenses, but there are recent EF-S lenses that eschew the short back design. The moniker now stands for “Small Image Circle”, as evidenced by this technical report.
(via The Digital Picture)