US 2019/0041605 A1↗2019Assignee: Canon Inc.Inventors: Shinichiro Saito, Makoto NakaharaCANON EF 400mm f/2.8 L IS III USM— 16 active elements / 12 groups (rear filter omitted), Patent f = 392.00 mm; traced EFL = 391.938 mmCANON EF 600mm f/4 L IS III USM— 17 ELEMENTS / 13 GROUPS PRODUCTION; 16 / 12 ACTIVE MODEL, 600mm f/4 MARKETED