CanonEF 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.

Works fine on my 70-200 lens, though it does drags a bit, focus is better, when the image is acquired, closer shots are much better than a distant shots. Considering, I had to manually focus the ver II, this is a god send. You will need to use your tripod of course. That will be my next big purchase, a strong tripod., for now, I ordered and tripod sack, attaches to each leg and you can put something heavy in it to better stabilize the tripod, if that works, I can put off buying an expensive tripod for a time... Took pictures of an eagles nest from across a lake, was full out on the lens, on a tripod, when the wind blew, the tripod shook just slightly, then to compensate, I took several burst of photo's, which dispite the wind, got a couple of keepers, with this I had to slow the shutter speed down, increased the ISO, as the eagle wasn't moving, it gave me better focused image. The 2x III, is better than Ver II, Focus is somewhat fasters, and images are more in focus.

I like this product a lot. For a drop in the bucket, you can effectively double the focal length of some of your white bodied canon L series lenses (I'm pairing it with an EF 70-200mm f2,8L IS USM). IQ takes a hard hit on the corners but is still decent in the center. AF works flawlessly so long as you had a sufficiently large aperture on the lens you're starting with (as this teleconverter brings the lens it's attached to two stops lower). Contrast also takes a slight hit. That said, the better the lens you pair this with, the better your results will be. I'm pleased enough with the product that I'm currently trying to figure out how to finance a 600 mm Canon lens instead of using it as a stopgap while I put together funding for a 400 mm Canon prime.Back to the way it's built: if you've ever owned an L series lens, you know the tolerances are very tight and that fit and finish is excellent. Indeed, often the easiest way to determine if a Canon professional or prosumer DSLR body has an L lens attached is to grasp the camera and lens in different hands and see if there's any motion or wiggle. If it wiggles, either you've got an old L lens that needs some work or you're using a non L lens. When connecting the teleconverter to my camera (5D Mark III), the teleconverter wiggles, and the lens on the other end of it wiggles with respect to the teleconverter.In conclusion: great product that solves many problems but lacks the fit and finish of the tools it's designed to function with.