Greetings. I am in the market for a teleconverter (TC-20E II) to use with my D300 and various Nikon lenses, 70-200mm f2.8 VR, 70-300mm f4.5-5.6 VR and if I get it 2nd hand a Nikon AF Nikkor 300mm f/4 IF-ED. I am of the understanding however that using a teleconverter will render ineffective the auto focus on a lens. I am wondering if my understanding is correct? Thanks in advance. Shootme...