Below is a hands on review of the Canon 200-400 F4 L IS with 1.4x extender Prototype by Joshua Holko
Canon 200-400 Pre-Production Sample Lens Review from Joshua Holko on Vimeo.
Pre Production prototype review of the new Canon 200-400mm F4L IS Telephoto Lens with inbuilt 1.4 teleconverter on the Canon 1DX camera with Landscape Nature and Wilderness Photographer Joshua Holko – www.photographyexpeditions.com