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):

The Canon EF 200-400mm f/4L IS USM Extender 1.4x costs a small fortune, but look at all you get for 12 grand. Find out how we rate it in our Canon EF 200-400mm f/4L IS review. What can you expect from a lens that costs about the same as a brand-new small family car?

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.

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!

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  Consistent Output, Fast / accurate auto-focus, Strong Construction

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  Heavy

I shoot a mixture of sports and wildlife. Previous to purchasing this lens, I used a combination of 300 2.8 IS and a 70-200 2.8 IS II on two bodies for most activities. I generally felt the 300 was too short a lot of the time and I also spent a lot of time switching between bodies to get close up...

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  Built-in Teleconverter, Fast / accurate auto-focus, Nice Bokeh, Rugged, Sharp, Zoom Super Telephoto

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  Hard 2 Zoom And Hold-hold

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.

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

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  on the heavy side