What are the differences between teleconverters and teleside converters?

Teleconverters and teleside converters are optical accessories that can be used to narrow the effective field of view of a lens.

Here are the main differences between teleconverters and teleside converters:

  1. Attachment: Teleconverters are attached between the camera body and the lens, while teleside converters are attached to the front of the lens. Teleside converters are afocal, which means they can be used with almost any camera lens that has a smaller front filter thread, with the help of adapter rings.
  2. Function: While teleside converters can narrow the field of view of a lens, they do not actually change the lens's focal length. Teleconverters, on the other hand, do increase the effective focal length of a lens.
  3. Impact on Aperture: Teleconverters reduce the maximum aperture of the lens by a certain amount depending on the magnification, typically one stop for 1.4x teleconverters or two stops for 2x teleconverters. This can affect the lens's low-light performance and depth of field. Teleside converters, on the other hand, do not affect the maximum aperture of the lens.
  4. Impact of Quality: Both types of converters introduce additional optical elements, they can potentially affect image quality by introducing additional aberrations, distortion, or vignetting.
  5. Impact on Focusing: Teleconverters can affect autofocus performance more because they reduce the amount of light that enters the lens, which can make it more difficult for the camera's autofocus system to accurately track a subject. Both do not change the minimum focusing distance.

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