Review on Canon Telephoto Extender Super Lenses by Glenna Naber

I've been using Nikon for a long time, the last camera was the D810. I was looking to upgrade to the D850 but chose the Sony A7R iii instead due to its form factor and the ability to use lenses with different mounts via adapters. Since then I have bought a Sony FE 12-24mm f/4, FE 24-105mm f/4 and a large number of Canon EF mount lenses in combination with a Sigma MC11 adapter. I will post my experiences with other lenses elsewhere. This review focuses on using Canon extenders with the EF 100-400mm II L lens on my system. Please note that all my conclusions are for my system only. Results may vary with other camera/lens combinations. I bought all three versions of Canon 1.4x extenders (used) to do a direct comparison with pictures of a brick wall. Since there is little point in using extenders at shorter focal lengths, I only made comparisons at 400mm for an effective focal length of 560mm. Below are my results.1. All three extenders had no autofocus issues on my system with no discernible difference. However, my main goal was to compare the image quality. I didn't do autofocus tests under difficult conditions.2. At all apertures (f/8, f/11 and f/16) 1.4x ii is only marginally better than 1.4x at any of the extreme angles. There will be no difference from real pictures. If you're considering buying used I wouldn't recommend paying significantly more for the ii.3 version. I also did an interesting test to find out how useful it is to even have an extender with a super sharp lens like the 100-400mm iil. I cropped the original image by 1.4x using Photoshop and then upscaled the cropped image to the original 42 megapixel image. I was shocked to see that the upsampled image was almost indistinguishable from the extender images. Of course, in the extreme corners you can find slight differences in detail (if you look closely!). But remember that with an extender you add size/weight, you lose a lens hood, not to mention the inconvenience of putting it on and taking it off when needed. I wouldn't use ver for me. me or ii on my system.4. As of ver. Third, I could easily see the extra sharpness on the extreme corners compared to previous versions. The middle looks about the same on all three versions. Needless to say, the upsampled image was worse this time. Again, the difference is not huge, but noticeable. If you need extra coverage, I recommend buying it (if you can afford it).5. I am planning a comparison with Kenko Teleplus Pro 1.4x DGX. I will update the review once the comparison is complete.6. I don't post pictures because the comparison only makes sense at full resolution.