Canon EF 2.0X III Telephoto Extender for Canon Super Telephoto Lenses

I got this to pair with my 70-200mm F/2.8 IS II since I needed a bit more reach, and didn't want to spring for a 300mm or 400mm lens.I'm extremely happy with it, and have to say that on a high quality lens, like the 70-200/2.8 IS II, there is hardly any loss of functionality at all. Yes, you do lose two stops, but getting a 400mm F/5.6 is not bad at all, and the 4 stops of the IS on the IS II certainly helps a lot. And these days, with the ability to shoot high ISOs without much noise (such as on the 5D3), it's not an issue getting clear shots at 1/500s or faster during the day.There is some SLIGHT image degradation, to be expected, but it is not noticeable at all unless you are seriously pixel peeping. Only at 100% crops would you be able to tell the difference, and the gain from the extra focal length far outweighs the slight loss in image quality.You do also get slower autofocus, again, because of the reduced effective aperture size (less light passing through, so it's harder for your camera to detect focus). The 70-200/2.8 IS II has extremely quick autofocus to begin with, so the reduced speed is not too bad. On slower autofocus lenses (such as if you use this extender for macro work, like on the 180mm F/3.5L Macro), the autofocus is nearly downright impossible and you may just be better off using full time manual focus.You also won't be able to use all the focus points that you're used to using, since you'll only be able to use the points that respond to f/5.6 or slower with a F/2.8 lens. On the 5D3, this means only the center rectangle of points (about 21 cross type points). The 1DS3 and 1DX give you a bit more focus point options at f/5.6. And on lower end cameras, you may be only able to use your center AF point.On slower lenses, such as f/4 or slower, you may be limited to manual focus only. That's why I really only recommend using a 2x extender on an f/2.8 lens. On slower lenses, you're better off using a 1.4x extender.The compact size and relatively light weight of the 2x extender makes it a must-bring any time I bring my 70-200 outdoors. Plus it gives me the flexibility of having either a 70-200/2.8 or a 140-400/5.6 at any time I want.It's especially great to use for wildlife (especially birds and other animals) and sports, if you're shooting during the day. For anything more serious, or in lower light, you'll need to spring for a 300/2.8 or 400/2.8, which are prohibitively expensive unless you're using it regularly for your full time job.

The quality is diminished a little bit using this, but I can't complain about it. I photographed Yellowstone National Park in August of '13, and used my 70-200 2.8 IS. So it became a 140-400 f/5.6. When I brought the RAWs into Lightroom and Photoshop, I could tell a very slight difference in both sharpness and contrast. I ran a denoise filter and adjusted with curves, and I honestly feel like my photograph is 98% as good as the Canon 400mm 5.6. This will not attach to a 100L macro, for that you'll need the 1.4 extender, but this will attach to a 180L macro, and it does not effect the minimum focusing distance. I had a 360mm f/7.1 with a 15 inch focus distance. At 7.1, it was still way too shallow! :) That's a great thing.I mainly photograph weddings, and found myself using this on a balcony in a large cathedral. It was a little difficult as I was stopped down to 5.6, but I shoot on a 5dm3, and was able to use a high ISO, so it wasn't too bad. I would have rather have had a 300 2.8, or even a 300 f/4, but the 5d3 does great with noise, so all the photos were fine. All that to say, if you're using this to shoot outside, you'll be totally fine. I still kept my ISO outside at 400 so I could raise my shutter speed. I noticed I was at 1/125 when it was cloudy, and that was just too slow for during the daytime. I still use this at weddings and other events, and with a little editing, you won't have any issues getting a good, usable photograph with this. I would be concerned to use this indoors, (like at a graduation or concert) unless you're experienced in that genre. But if you can't afford a 300 2.8, and need the reach, this'll help you out far better than 200mm and trying to crop it in tight. I'd much rather have 400mm with high ISO, and slightly lowered sharpness than 200mm, and cropped to 1/3 of it's original size.