Teleconverter between Nikon D50 and Tamron 70-300?

[SSJ]

I have a Nikon D50 with a Tamron AF 70-300mm Tele-macro lens that I use normally for wildlife and macro photography. My question is, rather than spend 1500.00 on a larger lens that I cannot afford for longer range shots, can I use a Tamron 1.4x or 2.0x teleconverter between them without compromizing clarity,and would it work in auto focus mode. This is my first DSLR and am having some good success with it. Any help would be appreciated

[stever]

the short answer is no, and no (autofocus only works to f5.6)

this lens (and all of the comparable lenses) are marginal at 300mm and don't do well with teleconverters

even a 1.4x will push it over the edge into generally unacceptable -- unless you're only lookiing for 4x6 snapshots

if you really need more reach, i'd suggest a Tamron 200-500 (which will probably be as good at 500 as your lens at 300), the Sigma 100-400 stabilized lens costs a little more but is probably more generally usable.  i don't think there is a 400mm prime lens for Nikon at a reasonable price available now.