All about Teleconverters

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....
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• Full Article Here from Mid Michigan Photography Club

And the a complete chart system of Nikon's Teleconverters summited by basegrinder...Here