In article <31A085AF.18F1@die.upm.es>, nieto@die.upm.es says...

>Does anyone have experienced comparing the AF Nikkor 300 IF-ED f:4 with
>the f:2,8?. Appart of the difference in the luminosity, is there any
>difference in terms of quality?.

I have used the Nikkor 300mm f4 AF and the Nikkor 300mm f2.8 AIS MF.
Both are good lenses, even wide open. The biggest difference between
them (other than the obvious speed/size/weight/price ones) is in their
differing capabilities with converters: the f4 is useable on the 1.4X,
but not great, but the f2.8 is really fine by only one stop down, and
is useable wide-open on a TC14C (with slightly inferior performance on
the TC14/14B) -- on the TC300/301, I would consider the f4 fair-poor,
but the f2.8 is useable wide-open, and excellent 2 stops down.
Hope This Helps