Canon EF70-200 mm f/2.8L IS II USM Instructions Manual page 17

14. Extenders (Sold Separately)
Lens specifications when using extender EF1.4x III or EF2x III are as follows.
Item
Focal length (mm)
Aperture
Diagonal
Vertical
Angle of view
Horizontal
Maximum magnification (x)
Attach the extender to the lens, and then attach the lens to the camera. To remove it, reverse the order.
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Errors may occur if you attach the extender to the camera first.
Only one extender can be used.
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Autofocusing is still enabled with Extender EF1.4X III/EF2X lIl attached.
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When an extender is attached, the AF speed will become slower to retain proper control.
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Extender EF1.4x III
98 - 280
f/4 - 45
25°20' - 8°50'
13°50' - 4°55'
20°50' - 7°20'
0.30
Extender EF2x III
140 - 400
f/5.6 - 64
16°20' - 6°10'
9°10' - 3°30'
13°40' - 5°10'
0.44
ENG-16