Review on Canon Telephoto Extender Super Lenses by Barbara Simmons

USM II lens. The Canon EF 1.4X III telephoto lens gives this lens a maximum focal length of 560mm f/8, so you lose a full stop. To put this in perspective, from f/5.6 to f/8 (one point) you get only half the light you get at f/5.6. I had a bit of a learning curve and had to fiddle with the settings a bit to get good exposure in low light. The day I got this was one of those overcast days where the sun looks like a speck in the sky, but I just didn't want to wait for better conditions, and really, why? It was actually a pretty good test. Five of the pictures I've attached were taken on that day; a fluffy woodpecker (picture 2), two eastern thrushes (picture 3 and 4), a pigeon (picture 5) and a crested tit (picture 6). My settings ranged from 1/200/ISO 1200 to 1/1000/ISO 800, with darker images at f/8. Most were filmed at an altitude of less than 60 feet, with birds in flight being over 150 feet +/-. All shots have been cropped to varying degrees, but I usually crop around 50% of the pixels. There is a slight IQ drop but nothing you will notice on the 11 x 17 inch prints below and for general use like facebook, forums and other places you may want to post images even if it is about high-quality images. After converting to JPEG or other lossy formats, this is a moot point anyway. at an increase over 100%, but honestly, how many people do that?. I don't see any color fringing or vignetting, although this has been reported, but I seem to be focusing on an object that I know is being cropped. I don't care if that's really the case. I've tested it with the mentioned 100-400mm lens on the 5D Mark IV, 7D Mark II (see revision) and Rebel T7i. All focus points worked on the 5D Mark IV and Rebel T7i, but only the two center focus points worked on the 7D Mark II. I tested in ambient light, which wasn't optimal. I'm really surprised because reviewers noted that you lose some peripheral focus points. Focus slowed down in low light on every camera I've tested, but to be honest it wasn't that bad. Good lighting is another matter, autofocusing on all cameras was fast as usual. Now that Canon says the Canon EF 1.4X III telephoto lens only works with certain lenses, it has nothing to do with optics or light, it just doesn't match other lenses. Just in case, I tried shooting it on the EF 70-300mm f/4-5.6 L IS USM II, EF 70-300mm f/4-5.6 IS USM II (not L) and EF 100mm f/2.8 (I know, just wanted to look) and it just didn't match the lens. The front element of the Canon EF 1.4X III telephoto lens is too deep into the lens to attach. This device will not replace a dedicated telephoto lens, but it will certainly increase coverage with very little IQ loss. You just have to choose your lighting battles. **EDIT 28th August 2019** My original review said the EOS 7D Mark II retained all focus points and while I can't explain how I missed it, you REALLY lose everything but TWO MEDIUM focus points with the 7D2, EF 100- 400mm L II and this extension, ie middle focus point and a smaller one in it. You can switch between these two, but the others are unavailable. I suspect it's a sensor and firmware issue, as the cheaper Rebel T7i resets focus points with no problem with this combination. My sincere apologies for misleading the owners of the EOS 7D Mark II.