For Nikon bodies we have had teleconverters that are 1.25x, 1.4x, 1.6x, 1.7x, 2x, and 3x available from Nikon or other vendors. Here are the changes each makes:
Note: “focal length changes” means that the equivalent angle of view decreases and the focal length changes by the specified amount (otherwise known as “equivalent” focal length).
1.25x converter (TC800-1.25E ED)
- Focal length changes by 1.25x
- Aperture increases by 2/3 stop
- Example: 800mm f/5.6 lens becomes 1000mm f/7.1
1.4x converter (TC-14a, TC-14b, TC-14e, third party converters)
- Focal length changes by 1.4x
- Aperture increases by one stop
- Example: 200mm f/2 lens becomes 280mm f/2.8
1.6x converter (TC-16a)
- Focal length changes by 1.6x
- Aperture increases by 1.3 stops
- Example: 200mm f/2 lens becomes 320mm f/3.2
1.7x converter (TC-17e)
- Focal length changes by 1.7x
- Aperture increases by 1.5 stops
- Example: 200mm f/2 lens becomes 340mm f/3.5
2x converter (TC-201, TC-301, TC-20e, third party converters)
- Focal length changes by 2x
- Aperture increases by two stops
- Example: 200mm f/2 lens becomes 400mm f/4
3x converter (no Nikon converters; Kenko Pro 300)
- Focal length changes by 3x
- Aperture increases by three stops
- Example: 200mm f/2 lens becomes 600mm f/5.6
Depth of field and other calculations are always made on the new changed focal length and aperture values. Thus, a 2x on a 200mm f/2 lens would cause the combination to function exactly like a 400mm f/4 lens (200mm x 2 = 400mm, two stops smaller than f/2 is f/4).
Note that the aperture must be f/8 or faster (after adjustment due to the TC) for the following cameras for autofocus to work: D7100, D7200, D7500, D500, D600, D610, D750, D800, D810, D850, D4, D4s, and D5. For all other Nikon DSLRs, the aperture must be f/5.6 or faster (after adjustment due to the TC) for autofocus to work.
Note further that some autofocus sensor positions become unusable as you get to f/5.6 and f/8 with a TC added. Consult the manual that came with your camera (or my Complete Guide for the camera) to learn about these restrictions.
