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A teleconverter is a nifty little piece of technology that can increase the focal length of your lens. It can be a very affordable alternative to buying a longer lens, but there are some drawbacks. Nikon and Canon make some very nice teleconverters specifically designed for their lenses. If you can't afford them, there are many third party converters that will fit a wide variety of lenses although they sacrifice some quality. Here's a look at some of the pros and cons of telectonverters.

Pros

Extended Focal Length

Having that extra reach when using a telephoto lens can really be helpful depending on the kind of photography you do. In situations where you're not able to get very close to your subject, like sports or wildlife photography, teleconverters can help you fill the frame with a more detailed photo. For those who are always itching to get a little bit closer, this could be your next investment.

Cost

Perhaps the biggest advantage is the cost. If money was not an issue then you could just buy a 500mm or 600mm lens. But for the money you could lay down on one of those you could also buy a used car. Nikon's recently announced 800mm lens has been reported to cost $18,000. So, you could buy that or buy a nice teleconverter for under $500 and attach it to a 400mm lens to get the same focal length. Though it obviously won't have the same quality, it's better than selling an arm and a leg.

Macro Ability

This advantage may be a little lesser known, but when you attach a teleconverter to you lens, you still keep the same minimum focusing distance. So you can increase the focal length without changing how close you can focus, enabling you to get close-up shots of your subject, possibly in the macro range depending on the lens.

Cons

Lower Image Quality

One of the major flaws of a teleconverter is the degradation of image quality. It can lower sharpness and contrast while also magnifying abberations. Though you can't avoid these flaws completely, you can minimize them by using a high-quality prime lens, a high-quality TC specifically designed for the type of lens you have, and by using shorter teleconverters.

Loss of Light

Another disadvantage of using a teleconvter is that is reduces the amount of light that enters the camera. For a 1.4x TC, you lose one stop of light. For a 2x TC, it's two stops. This means that slower shutter speeds are inevitable.

Focusing speed

Along with the loss of light, focusing speed is also affected. How much it's affected depends on the lens and the scene you're shooting. On certain lenses, the autofocus won't even work if it reaches past a certain max aperture. Many will have a hard time focusing after the calculated max aperture reaches f/8 or smaller. It is recommended that a prime lens with a large max aperture is used, like a f/2.8 or f/4.

Overall

Teleconverters are a very affordable way to increase the focal length of your lens. But what you gain in functionality, you lose in image quality and focusing speed. Using a high-quality fast prime lens, a brand appropriate TC, and avoiding using longer teleconverters, like a 3x, will assure that you minimize the disadvantages. Of course, investing in these things also costs more money, the root of all our photography problems.

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Written by Spencer Seastrom