Excerpt: I use this lens with a Canon 70-300mm lens.The Kenko gives automatic focusing up to about 200mm,but from there to 300mm it does not.One must focus manually in this region-which is no big problem.The teleconverter is well made and has the look of qualityI would recommend it.
Pros: Easily Interchangeable, Fast / accurate auto-focus, Lightweight, Rugged, Strong Construction
Excerpt: I have excellent results with this converter using my Nikon 300 f4 lens, even hand held most of the time. I shoot with a Nikon D3s so I do push the ISO up to keep my shutter speeds over 600. Technique is key with this combo. It doesn't work with my 80-400 over 300mm zoom.
Pros: Consistent Output, Fast / accurate auto-focus
Summary: I am using this with a Nikon 80-200 F2.8 AF-D which makes the lens a 160-400 F5.6 and I have no complaints. I wish Nikon had and auto focus teleconverter that fits this lens, but all their new teleconverters are for AF-S lenses.