In article <32580C5D.62AB@erols.com>, rejames@erols.com says...

>Looking for a good 300mm f2.8 auto focus lens for a Nikon N90. Can't
>afford a new Nikon lens. Having trouble finding good used
>Nikon/Nikkors. Does anyone have personal experience using Tamron or
>Sigma as substitutes? How good were your results?

The point of lugging around a 300mm f2.8 is to be able to use the
lens at f2.8 (otherwise, the Nikkor AF 300mm f4 is far smaller,
lighter, cheaper - and it is really excellent at f4). I would be
inclined to wait for the affordable used Nikkor, if high-quality
performance at f2.8 is essential....
Hope This Helps