Canon officially released the EF 200-400mm f/4L IS USM Extender 1.4x lens in July after announcing its development over two years ago. The new lens has garnered raved reviews (including yours truly) and the EISA lens award for 2013.
Although Canon has been experimenting on Super Telephoto lens with built-in extender since the 1980s (read my article above), Egami, the Japanese Photography blog has uncovered an additional Canon patent for this technology. Specifically, a patent for the EF 300-600mm f/5.6L IS USM Extender 1.4x lens.
Personally, I am not too excited about this new patent because the lens will be quite heavy and slow (f/8) once the extender is deployed. The current EF 200-400mm f/4L lens weighs almost 8 pounds already. The lens I am more interest in is the EF 400mm f/4 DO IS II lens. The current 400mm DO lens is one of my favorite wildlife lenses but the design is over 12 years old and needs an upgrade to take advantage of the latest technology in materials and optics.
Canon is trying to start 2014 with a re-invigorated beginning by introducing exciting and useful equipment. I have been a Canon user for 25 years and have made some observations on the company recently. Coming out with a new 400mm DO lens will go a long way to accomplish this goal and excite the photography community.