Canon EF 200-400mm f/4L IS USM Extender 1.4x

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Zoom lens

A zoom lens by Canon for Full frame cameras, 200-400mm f/4. A professional wildlife zoom with a built-in 1.4x teleconverter.

What it frames like

Its full-frame-equivalent focal length on the sensor it was made for.

How wide 200mm sees at its wide end on each sensor it covers.

f/4 wide open, to scale against f/1.4.

On full frame (Canon EF): as marked, 200-400mm.
On APS-C (Canon) (Canon EF): like 320-640mm on full frame; f/4 gives about the depth of field of f/6.4 there.