Usable lenses:

Lens	Focal Length & Maximum Aperture
	EF1.4X III	EF2X III
EF 135mm f/2L USM	189mm f/2.8	270mm f/4
EF 180mm f/3.5L Macro USM	252mm f/4.5	360mm f/6.7
EF 200mm f/2.8L USM	280mm f/4	400mm f/5.6
EF 200mm f/2.8L II USM	280mm f/4	400mm f/5.6
EF 200mm f/1.8L USM          *	280mm f/2.5	400mm f/3.5
EF 200mm f/2L IS USM	280mm f/2.8	400mm f/4
EF 300mm f/4L USM	420mm f/5.6	600mm f/8
EF 300mm f/4L IS USM	420mm f/5.6	600mm f/8
EF 300mm f/2.8L USM          *	420mm f/4	600mm f/5.6
EF 300mm f/2.8L IS USM	420mm f/4	600mm f/5.6
EF 400mm f/5.6L USM	560mm f/8	800mm f/11
EF 400mm f/4 DO IS USM	560mm f/5.6	800mm f/8
EF 400mm f/2.8L USM          *	560mm f/4	800mm f/5.6
EF 400mm f/2.8L II USM       *	560mm f/4	800mm f/5.6
EF 400mm f/2.8L IS USM	560mm f/4	800mm f/5.6
EF 500mm f/4.5L USM          *	700mm f/6.7	1000mm f/9.5
EF 500mm f/4L IS USM	700mm f/5.6	1000mm f/8
EF 600mm f/4L USM             *	840mm f/5.6	1200mm f/8
EF 600mm f/4L IS USM	840mm f/5.6	1200mm f/8
EF 800mm f/5.6L IS USM	1120mm f/8	1600mm f/11
EF 100-400mm f/4.5-5.6L IS USM	140-560mm f/6.7-8	200-800mm f/9.5-11
EF 70-200mm f/4L USM	98-280mm f/5.6	140-400mm f/8
EF 70-200mm f/4L IS USM	98-280mm f/5.6	140-400mm f/8
EF 70-200mm f/2.8L USM	98-280mm f/4	140-400mm f/5.6
EF 70-200mm f/2.8L IS USM	98-280mm f/4	140-400mm f/5.6
EF 70-200mm f/2.8L IS II USM	98-280mm f/4	140-400mm f/5.6
EF 300mm f/2.8L IS II USM	420mm f/4	600mm f/5.6
EF 400mm f/2.8L IS II USM	560mm f/4	800mm f/5.6
EF 500mm f/4L IS II USM	700mm f/5.6	1000mm f/8
EF 600mm f/4L IS II USM	840mm f/5.6	1200mm f/8
EF 1200mm f/5.6L USM       *	1680mm f/8	2400mm f/11

*: Using an Extender with this lens may result in incorrect autofocus.
    If your camera has an AF microadjustment function, do the AF microadjustment.
    If your camera does not have an AF microadjustment function, focus manyually if the AF precision is way off.

• For details on AF microadjustments, see the camera's instruction manual.
• Refer to the camera and lens instruction booklets to see if there are any AF compatibility limitations.
• The maximum aperture is indicated in half-stop increments.

Maximum Aperture with the Extender

When Extender EF1.4X III is attached, the lens maximum aperture will be smaller (darker) by 1 stop. With Extender EF2X III, the maximum aperture will be smaller by 2 stops. In any case, the camera will compensate the exposure automatically.

Caution

• Do not attach two or more Extenders on the same camera. Doing so will degrade the optical performance and the camera will not be able to obtain proper exposure readings.
• To enhance water and dust resistance, the Extender EF1.4X III and EF2X III have a rubber ring around the mount. As the lens is repeatedly mounted and detached, the rubber ring will leave fine abrasion marks on the outside of the camera mount. This will not affect operation
  The rubber ring can be replaced by a Canon service center (a fee will be charged).
• Autofocusing slows down when the lens is used with an extender, in order to maintain the precision of autofocus control.
• The Extenders cannot be used with film cameras other than the EOS-1V. Using an Extender with a film camera other than the EOS-1V may cause misoperation.