Excerpt: Entry into the long telephoto arena is very costly (10-12K for 500 or 600mm IS-2) and for many is not frequently needed. As an owner of several Canon lenses (300mm f4/L is, 100-400mm is-1, 400 f/5.6L and 100-400mm IS-2)I noted photos with the 1.4xIII extender were good with both the 300mm f/4L is...
Excerpt: Wont work with (white box) adjustable lenses, only (red dot) lenses. Doubles magnification, definitely requires tripod and remote shutter control, no movement at all to get a clear picture. Wildlife photos.
Excerpt: I wanted this for wildlife. It says it communicates between lens and camera and it doesn't work the way it was advertised. I use it with the EF 100-400mm f/4.5-5.6L IS USM lens and now I see it will not auto focus.
Summary: This is a superb extender which works flawlessly with the Canon prime telephoto and super telephoto lenses. I bought it to supplement my Canon 300 mm f/2.8 IS II lens to give me an effective 600 mm f/5.6.
Pros: Very cost effective way of increasing your telephoto reach. It's very light and compact.
Cons: Loss of two stops of light compared with the mated lens.
Excerpt: There are a good many pros and cons to using this product, first, the cons. It slows down the auto-focus of my lenses to the point that I wonder if they are even working at times. The auto-focus in poor light is even worse, and I miss a good many more photos when using this 2X extender.
Excerpt: I purchased this to add length to my 100-400 f4-5.6L. So far the results have been mixed. I've not gotten the quality of results I seek as the images I'm getting have been less than tack sharp.
Excerpt: Good quality, good price, but not very usable with several of my EF-L lenses because of minimum aperture requirements. With the 2-stop loss of light, any lens with a native aperture of 5.6 or smaller won't autofocus at all (with my 40D and 6D Canon cameras.