Canon Ef 1.4x Iii Extender

Brand	Canon
Manufacturer	Canon
Model Number	EF 1.4 X III

The Canon EF 1.4x III Extender is a small and light addition to your kit that extends the focal length of a compatible lens by 1.4x. Downsides to using an extender include decreased aperture and decreased autofocus speed. Additionally, the extender does not affect the MFD (Minimum Focus Distance) of the lens it is mounted behind.

The Canon EF 1.4x III Extender mounts between your Canon EOS Digital SLR and a compatible lens (primarily Canon L Series lenses), extending the focal length of the lens by a noticeable 1.4x. The 1.4x III is a small and light addition to your kit, an only moderate hit on your wallet and it provides a noticeable increase in your focal length. Sounds like a great deal, but this (and all) extenders are not completely without downsides which I'll discuss throughout the Canon EF 1.4x III Extender review.
 
The primary reason to use any extender is of course to gain a longer focal length/narrower angle of view from a lens - to frame the subject more tightly. Here is an example of the focal length increase provided by the 1.4x and 2x extenders. The above images (of a Christmas Cactus flower) were taken from the same tripod-mounted position (using the tripod ring) with a Canon EF 180mm f/3.5 L USM Macro Lens on a Canon EOS 5D Mark II camera body. The difference in framing (angle of view) is quite noticeable between the three examples shown. This is the lone, but significant, advantage provided by extenders.
 
Use of a 1.4x extender (any brand or model of them) decreases/narrows your lens' max aperture setting by 1 stop - allowing at most 1/2 as much light into the exposure. The lens aperture still opens to the same physical diameter, but the ratio of the aperture opening to the focal length is reduced - by 1 stop. So, pick your lens' maximum aperture opening from the following list and understand that it will shift one value to the right when any 1.4x extender is attached: f/2.0, f/2.8, f4.0, f/5.6, f/8.0.
 
Add the focal length multiplier and max aperture reduction together to get your resulting lens equivalent. For example, a 1.4x extender (also commonly referred to as a teleconverter) makes a Canon EF 70-200mm f/2.8 L IS II USM Lens into a 98-280mm f/4 IS lens (yes, IS still functions normally on all compatible IS lenses). A Canon EF 70-200mm f/4.0 L Lens mounted over a 1.4x becomes a 98-280mm f/5.6 lens. A Canon EF 300mm f/2.8 L IS Lens becomes a 420mm f/4 IS lens. And, as shown in my Canon EF 1.4x III Extender review examples above, the Canon EF 180mm f/3.5 L USM Macro Lens becomes a 252mm f/5.0 USM Macro Lens.
 
DSLR cameras will continue to calculate auto exposures properly when used with Canon Extenders.
 
Though most extender-compatible lenses have max apertures of at least f/4, some of the longer ones have an f/5.6 native maximum aperture (such as the Canon EF 100-400mm f/4.5-5.6 L IS USM Lens between 260mm and 400mm). Since most non-1-Series Canon EOS camera bodies need a max aperture of f/5.6 or wider to autofocus, only Canon 1-Series camera bodies can autofocus (using the center AF point only) these f/8 max aperture, 1.4x combinations. The lens and extender combo can always be used in manual focus mode, but remember that a narrow max aperture creates a dark viewfinder that makes manual focusing difficult.
 
Extenders do not affect the MFD (Minimum Focus Distance) of the lens they are mounted behind, so the MM (Maximum Magnification) of the lens is also multiplied by 1.4x. Do you need more macro magnification from your Canon EF 180mm f/3.5 L Lens? Add the Canon EF 1.4x III Extender to the setup for a 252mm 1.4:1 (1.4x) Macro lens.
 
Shooting with the Canon EF 1.4x III Extender mounted results in reduction of autofocus speed. According to Chuck Westfall (Canon USA): "As with previous EF Extenders, usage of Series III EF Extenders lowers AF drive speed to improve AF performance. When Extender EF 1.4X III is used, AF drive speed is reduced by 50%. When Extender EF 2X III is used, AF drive speed is reduced by 75%. This may seem like a drawback, but in reality subject tracking performance remains quite high when Series III Extenders are used with IS II lenses. This is due to improvements in AF precision made possible by the new microcomputer in the extenders."
 
With good lenses mounted, I'm not having any tr