In article <49tvpe$6la@newsbf02.news.aol.com>, libby35mm@aol.com says...
>I am a Nikon user dedicated to Nikon lensesbecause I find them >excellent and sharp for nature photography and macro work. Purchased >new Tamron 200-400 in June for large wading birds, disappointed >because of fade-out (unsharp) at edges; poor performance (fuzzy images) >w/ NIkon 1.4 converter; flatness or non-dimensionality of bird photos; >and blueish cast. Agree? Disagree? Any suggestions for a long lens >(400+) which is sharp with converter and doesn't cost the National >Debt?

The older (larger) version of the Nikkor 500mm f8 mirror is relatively
inexpensive used (I prefer it in performance to the newer, smaller,
closer-focussing version, though for close work, the newer version
may be preferable), and is surprisingly sharp on the TC14/14B
converter (which also reduces the mirror "hot spot"). It is very
slow (slower than rating - and is best used with the ASA set 1/2
stop lower [overexpose 1/2 stop from meter reading]), and the
"doughnuts" may not amuse you - but for a lens that is long, high quality, and affordable, it is hard to beat.
Hope this helps.