Canon EOS Academy photography workshops are my best place to counter various customers’ queries.
They say that in some shooting situations the lens they have simply just not have a long enough focal length for the picture they want to take.
So they ask me if there a way which can compensate the investment on lenses which are longer, heavier and more expensive?
The answer to this question is Canon's EF Extenders which offer a simple way to multiply the focal length of your lens.
They are available in two multiplication factors – 1.4x and 2x.
Who is it for?
The Canon EF1.4x III and EF2x III extenders are for use by anyone who wants a bit more reach from their lenses. The most likely candidates to require them for regular use
are wildlife and sports photographers
Key features
1. Dust and moisture resistant
2. Extends the lens focal length by 1.4x or 2x
3. Very high quality optics to maximise lens performance
4. Integrated processor to transfer all lens and focusing information
5. Internal baffles to reduce inner reflections for higher image quality
Limitations
Maximum aperture
Extenders are a relatively cheap and convenient way of enhancing telephoto capabilities. But, increased focal length comes at a cost − maximum aperture.
The 1.4x Extender causes a decrease of one stop in the maximum aperture of the lens, while the 2x Extender causes a loss of two stops. This means you gain extra focal
length at the expense of losing some light.
For example, if you attach a 1.4x Extender to an EF70-200mm f/2.8L IS USM lens, for example, it will become a 98-280mm f/4 lens.
Autofocus with Extenders
Apart from reduced maximum aperture, another potential drawback of using Extenders is loss of autofocus.
On most cameras, autofocus stops when the maximum effective aperture drops below f/5.6, irrespective of the amount of light available. However, there are some EOS
models that allow auto focusing at maximum apertures down to f/8. Example: Canon 7D, 5D Mark III and 1Dx.
Autofocus speed
Even if autofocus still functions when you fit an Extender to one of the compatible lenses, the autofocus speed may be reduced.
Minimum focusing distance with extenders
Extenders do not affect the MFD (Minimum Focus Distance).If you're looking to get closer to your subjects without investing in a longer lens, the extender is worth a look.
Compatibility
Not all Canon lenses accept Canon Extenders. This is due to their construction. Extenders have a protruding front element that will not fit into the rear of many EF lenses.
Compatible lenses have a recessed rear element, which creates space for the front element of the Extender.
Mark III Extenders
The latest Mark III Extender features a new integrated micro-processor chip to provide complete communication between lens and camera and ensure that the focusing can
be completed as quickly as possible.
Note: So that the Extender-Lens combination is reported correctly the Extender should be fitted to the lens first before attaching the whole combination to the camera.
Key Technologies
Internal reflection coatings
The EF Extenders featured high levels of internal reflection baffling to stop stray light bouncing around within the extender body and thereby affecting image quality.
Weather sealing
Both extenders feature dust and weather sealing to maintain the high levels of weather sealing provided by the Canon L-series lenses and the EOS-1 series cameras
Fluorine lens coating
In the quest to keep the lens elements clean and thereby realize the best image quality possible, the front and rear lens elements have been coated with Fluorine.
Extender EF1.4X III
Extender EF2X III
Information transmission between the lens and extender as well as between the extender and camera
500mm
700mm
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