How do teleconverters work in terms of losing light?

[mikoh4792]

If I were to pair a nikon 70-200 F4 with the TC-14eII or III, what would the maximum aperture be since I lose one stop of light? Would it be f/5.6?

 

[480sparky41 41]

Yep.

 

[KmH]

A stop is a halving or a doubling of the amount of light.

A 1.4x TC will 'cost' you 1 stop of lens aperture so yes, f/4 - 1 stop = f/5.6.
A 1.7 x TC will 'cost' a stop and a half. f/4 - 1.7 of a stop = f/6.7
A 2x TC 'costs' 2 stops. f/4 - 2 stops = f/8

Note: Because they are fractions f/5.6 is a smaller number, and a smaller lens aperture, than f/4.