This tele extender can be used with fixed focal length lenses 135mm and longer (except the 135mm f/2.8 Softfocus lens), and the EF 70-200 f/2.8L, 70-200 f/2.8L IS, 70-200 f/4.0L, and 100-400 f/4.5-5.6L IS zoom lenses.
Superb optically, it preserves the image quality of the lens it's mounted to and multiplies its focal length 1.4x.
Effective aperture is reduced by one f-stop; autofocus is possible on any EOS camera when combined with a lens having an f/4 or faster maximum aperture.
The new version II maintains the outstanding optics of the previous version, and adds enhanced weather- resistant construction, and improved anti-reflective surfaces in the barrel.
(When used with EF Extender EF 1.4x II, the EF100-400mm f/4.5-5.6L IS USM lens is compatible for auto exposure with all EOS cameras.
However, you lose autofocus with all EOS cameras except those with a 45-point AF system, such as EOS-3, EOS-1v, EOS-1D, EOS-1Ds and EOS-1D Mark II. Only the center focusing point is functional when this lens/extender combination is used with the 45-point AF cameras.
Also, when the EF100-400L is used with the EF 1.4x II, the Image Stabilizer function does not work with older EOS 35mm cameras such as the EOS 650, 620, 630/600, RT, 700, 750, 850, EOS-1, A2/A2E, 10s, Elan, Rebel/Rebel S, and Rebel II/Rebel SII.)