The examples below give some idea of the lens's zoom range, shot from the same position on the EOS-1D X at 200mm, 400mm, and 560mm (i.e. with 1.4x extender engaged):

Causing great excitement among Canon photographers was the February 7, 2011 development announcement of the Canon EF 200-400mm f/4L IS USM Ext 1.4x Lens. I was personally excited – a Canon EF 200-400mm f/4L IS USM Lens had long been on my most-wanted Canon lens list.

A great sensation for the optical world, this super telephoto full-frame stabilised zoom lens opens a new era for professional optics. The Canon EF 200-400mm F4L IS USM Extender 1.4x has a built-in teleconverter, that allows the photographer to switch to extended focal lengths in just a second.

Canon's EF 200-400mm f/4L IS USM Extender 1.4X more than satisfies the requirements of its target market. Sports and wildlife photographers should be delighted by the convenience of the built-in extender and the fact that it doesn't compromise image quality.

My photography has changes since I bought this lens. I now shoot more sports and wildlife. The lens is very good for everything that has action.For football I can go sit in the end zone and cover the entire field from the far end zone to 10 yards out.

I was lucky enough to get a loaner 200-400 from Canon CPS. I found the image quality to be outstanding. The lens focus is super fast... I found it to be on par with my 400 prime, which focuses as fast as any lens I've used.

Best lens I've ever used for aviation photography. All of the versatility needed to capture images in any setting, and the built-in converter loses almost nothing I can detect in terms of image quality or focusing speed.

• +

  Fast auto-focus, Superior build quality, Super-sharp images, very verstaile telephoto range, built-in teleconverter

• -

  on the heavy side

The optics are tremendous and when paired with the new 1dx the images are stunning. I have shot mostly wildlife and some sports. You can hand hold a few shots with high shutter speeds but this is meant to be used w/ a monopod or tripod.

This Lens is my primary wild life lens, after a lot of deliberation between the 400 f2.8 and 200-400 f 4 I decided on the 200-400 for its versatility. I have the ability to zoom and switch to built in 1.4 without having to remove the lens.

Brilliant lens !! I am an aviation photographer and just got back from a shoot in California with the U.S. Navy.Used it with and without extender without change in results. Is it a little heavy? Yes but I had no problem hand holding it for most of the day in windy conditions.

As a sports shooter, I carry this lens everywhere. It covers from 200mm-560mm( within extender). When I move by plane, I can bring the equipment easily in a jet.This lens is the strongest partner for sports shooter, wildlife and news. You don't loose the chance with it.

I get my chops broken by other parents when I show up with this lens on my 1DX or 1DC at my sons football games but when the parents and coaches see the end result with the shots that I get they soon realize what it takes to make those NFL quality images look awesome!

This lens is amazing, delivery quality image as any prime lens, plus the feature that let you work in composition. This lens (200-400 f4) do the job of 200mm,300mm and 400mm primes 2.8mm. The only difference is the aperture (a little more than 1.2mm less of those three).

Took it out immediately and shot with internal and external Extender(784mm-f13-1/1250-ISO1000-5DMkiii), I figured this should stretch the test. If I wasn't pleased it was going back! I kept it and am thrilled with the performance. The sharpness blew me away!