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What is a teleconverter?

Answer provided by Penny Verran. Photos by Mike Collins.


This articles has been adapted from Penny's original PowerPoint presentation.

What is a teleconverter?

  • An optical device that fits between your camera body and the lens.
  • Increases the effective focal length of a lens.
  • Also called a tele-extender, converter or extender.

Magification Factors

  • 1.4x is equivalent to a 40% lens extension. For example, a 200mm lens becomes the equivalent of a 280mm lens.
  • 1.7x (Nikon) is equivalent to a 70% lens extension. For example, 200mm lens becomes the equivalent of a 340mm lens.
  • 2x is equivalent to a 100% lens extension. For example, 200mm lens becomes the equivalent of a 400mm lens.

Various Teleconverters

  • Dedicated Units
    • Available from major camera manufacturers.
    • Designed to match certain lenses.
    • Best results.
    • More expensive.
  • Universal Models
    • Work on any lens on which they can be mounted.

Nikon teleconverters
Figure 1: Nikon teleconverters (1.4x, 1.7x, and 2x).

Teleconverter Mounted to a Lens

Teleconverters are mounted between the camera body and the lens being used.

Nikon F6 with 105mm lens and a 1.4x teleconverter
Figure 2: Nikon F6 with 105mm lens and a 1.4x teleconverter.

Pros and Cons of Using Teleconverters

  • Pros
    • Offers photographers the ability to shoot at increased focal lengths without buying a completely new lens.
      • Cost saving method.
      • Camera specific teleconverter prices can range from $285 to $439.
      • Universal teleconverter prices can range from $149 to $210.
      • New lenses with the same effective focal lengths can cost thousands of dollars.
    • An excellent way to increase image size without having to get closer to the subject.
      • Use when you want to make a long focal length lens into an even longer focal length.
      • Ability to get more closely framed shots (example: a full body shot vs. a tightly framed upper body shot).
    • Use when you want to increase magnification when you’re doing a close-up.
    • Improved mobility for photographers.
      • Convenient to use.
      • Compact size.
      • Light weight.
      • Easier to carry.
  • Cons
    • Light loss
      • Teleconverters not only multiply the focal length, but also multiply the f-stop by the power of the teleconverter.
        • F-stop progression is increased by a power of 1.4 (each f-stop is 1.4 times the preceding one).
        • When the focal length is multiplied by 1.4, the aperture decreases by one stop. For example, f/2.8 becomes f/4.
        • When the focal length is multiplied by 2, the aperture decreases by two stops. For example, f/2.8 becomes f/5.6.
      • May force you to use slower shutter speeds than you prefer. (To solve this problem, you can increase the ISO sensitivity (digital) or use faster film to decrease the effect.)
      • May cCause you to lose the auto focus function.
        • Most auto focus systems require a minimum light level of f/5.6.
        • At any slower aperture, the auto focus system shuts off.
      • May decrease focusing speed.
    • All teleconverters magnify defects, optical aberrations and lack of sharpness.
    • They also magnify any movement in the camera, also known as camera shake. (You may increase shutter speed & use a tripod to decrease the effect.)
    • All of these factors contribute to a decrease in overall image quality.

Example Photographs

This series of photographs were taken from the same distance show the effects of using different teleconverters.

Photographed with a 105 mm lens and NO teleconverter
Figure 3: The Elusive Mammalian Picnic Table Fish photographed with a 105 mm lens and NO teleconverter.

Photographed with a 105mm lens with a 1.4x teleconverter
Figure 4: The Elusive Mammalian Picnic Table Fish photographed with a 105 mm lens and a 1.4x teleconverter.

Photographed with a 105mm lens with a 1.7x teleconverter
Figure 5: The Elusive Mammalian Picnic Table Fish photographed with a 105 mm lens and a 1.7x teleconverter.

Photographed with a 105mm lens with a 2x teleconverter
Figure 4: The Elusive Mammalian Picnic Table Fish photographed with a 105 mm lens and a 2x teleconverter.

Tips for Using a Teleconverter

  • Check compatibility with lenses before using teleconverters.
  • Use the fastest/best prime lens you can.
  • Avoid using zoom lenses, if possible.
  • Use a 1.4x vs. a 2x teleconverter (better quality).
  • Use the best photographic technique you can.
  • Maintain a relatively fast shutter speed.
  • Increase the camera ISO (digital) or use faster film.
  • Take advantage of the lens' close-focusing ability for framing small subjects.
  • Shoot with a tripod to eliminate camera shake.

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