Extender lens is photographic accessories serve to extend the range of the focal length of a lens. Extender / teleconverter mounted between the camera body and lens, and like a lens has elements in it that can increase the magnification (magnification) of a lens. This article will explain the functions and properties of extender or teleconverter for Canon, but in general the rules and theory also applies to Nikon lenses.
Two Extender / Teleconverter Canon Made

Canon sells two types of extender / teleconverter lens, Canon EF 1.4x first is the Mark III and the second is the Canon EF 2x Mark III. Both types of extender is designed for use on artificial Canon telephoto lens. Both use technology such as lenses that can keep the quality of the image that is not too drop. In addition to optical elements, they also have electronic components and communications processor to connect between the lens and the camera body. What are the consequences? both are quite expensive. In Indonesia, two teleconverter will cost each about Rp. 4 Million.
Function Extender / Teleconverter

As already mentioned above, the lens extender function primarily increase the range of focal length telephoto lens. When fitted to a 300mm lens EF 2x extender Mark III, the lens focal length is effectively changed to 600mm. In addition there are some consequences that you need to understand the following.

As an illustration, the third photo shows how the extender / teleconverter lens works further the focal length range. The first picture without using extender / teleconverter lens (300mm lens):
Photos with extender / teleconverter 1.4x III and EF 300mm lens
By using extender / teleconverter EF 2x III and 300mm lenses
Another consequence A Lens Extender

Both Canon extender on maintaining all communication between the lens and the camera, so the autofocus and IS (Image Stabilization) continue to work normally. Although, the autofocus motor speed can be reduced. Minimum Focusing Distance will not be affected.

No extender is perfect, and any extender will always reduce the overall photo quality.

In addition, the extender will also narrow maximum aperture lens. Canon Extender EF 1.4x III could reduce the maximum aperture by one stop. While EF 2x III will reduce the maximum aperture by two stops. If the term stop making you confused, please read the terms of the stop in photography.
And Autofocus Lens Extender

The consequences of the extender which reduces stop is the cessation of effective aperture time autofocus performance drops below the limit. At an average of Canon cameras, while the maximum aperture down into smaller (his bigger f number) below f/5.6, so autofokusnya will stop working because not enough light into the sensor so that the autofocus performance impaired. For example, when mounted on a 300mm lens f/2.8, EF 2x extender will add twice the focal length, but reduces the maximum aperture by two stops so a 600mm f/5.6 lens.

An easy way to understand the above explanation: when you use the Canon Extender EF 1.4x Mark III, so autofocus still work, just be sure to use a compatible lens has a maximum bukaaan f / 4 or larger (f/2.8, f / 2). When you use Canon EF 2x Mark III, make sure you wear lenses that are compatible with the extender and also has a maximum aperture of f/2.8 or larger.
Extender Lens and Canon Tele Lens compatibility

Extender is compatible with all Canon lens EF prime lens%
Alternative Lens Extender

Kenko make some teleconverter (extender) for Canon and Nikon, and is designed to be used by the EF lens with a focal length of 100mm above the optimal, but more used focal lengths between 200 and 400mm. Kenko Teleconverter cheaper, about USD 1.5 million and still maintain electronic communication between the lens and the camera, so the autofocus and IS / VR continue.


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