Sat 22-Sep-12 10:27 PM | edited Sat 22-Sep-12 10:30 PM by GiantTristan
You cannot fit a Nikon TC on the 18-200 lens which is f/5.6 at its long end. If you find a third party TC that would fit, the lens will even become slower. I suggest that instead of buying a new camera body, you might want to get a 70-200/2.8 VRII lens which works well even with a 2.0 Nikon TC. This will give you a 400mm lens with f/5.6. The TC 1.4 will give you a f/4.0 lens, the TC 1.7 a f/4.8 lens. To save some money, try to get a used VRI version of the 70-200/2.8 lens. Aside from compatibility with TCs, this lens will give you much improved IQ, faster AF and a much brighter view finder.
I have had my 70-200/2.8 VRI for about seven years and used it on D70, D200, D700 and soon D800. It is much wiser to invest in good lenses than in camera bodies - camera bodies become "obsolete" after a couple of years, while good glass lasts forever and seldom depreciates.