Why Use a Teleconverter?
Most photographers carry a telephoto lens in their kits. These lenses are great for getting up close and personal to subjects when it is impractical to physically move closer. There are times, however, when even our strongest telephoto does not get us close enough to the action and we need just a little more of a zoom. One option is to invest in a new and longer lens, though this solution can be expensive and is not always a viable option. A cheaper way to extend the focal length of any lens is to buy a teleconverter (or extender). A teleconverter looks like a compact lens and is mounted between the camera body and the lens. It multiplies the focal length of the lens it is connected to. Teleconverters range from 1.4x magnification to 2x magnification.
The Benefits of a Teleconverter Lens
These tools work great in some circumstances:
The most obvious reason to use a teleconverter is to increase your focal length. A 2x converter will double your focal length, taking a basic 70-200 mm lens up to 150-400 mm.Teleconverters do not weigh a lot, but professional telephoto lenses often do. For example, Canon’s 100-400 mm lens weighs 1,363 grams (about 3 pounds).Using a teleconverter does not affect your minimum focusing distance. This means that you can continue to use a telephoto lens to get close-in to a subject that is not too far away.
The Drawbacks of a Teleconverter Lens
However, teleconverters aren’t ideal in other circumstances:
Using a teleconverter can drastically reduce the speed of your lens. The lens receives less light with a teleconverter, reducing the maximum available aperture. With a 1.4x converter, you will lose one stop, and with a 2x converter, you’ll lose two. Sharpness and contrast can suffer when using a teleconverter, multiplying any small imperfections that your lens might suffer. Teleconverters work best with high-quality glass. Increased focal lengths intensify camera-shake problems. Teleconverters can slow down the speed at which your camera can focus. If you have an entry-level DSLR, you might find that it cannot autofocus at all with a teleconverter.
Final Thoughts on Teleconverters
If you own a cropped-frame camera, your focal length will already be magnified by around 1.6, so it is possible to get a very long lens! Not all lenses are compatible with teleconverters, so check your lens’ compatibility before investing in a teleconverter.
