>>I was tempted to reply that if you don't need f2.8 for >either >>low light, subject isolation, or AF with TC's, why on >earth >>other than ego, would you carry it around - assuming there >was >>a viable f4 alternative of similar IQ? >> >>But, then I remembered: You get a noticeably brighter >>viewfinder from f2.8 than from f4. That is a real >practical, >>as well as a comfort, advantage to a lot of us. Once you >get >>used to that, it's probably hard to give up. Also, all >other >>tings being equal, AF should be faster with more light >from >>the f2.8 lens. I don't know that for certain, but it's >>consistent with what I do know about how AF diminishes >with >>poorer light. >> >>I know that when I put away my fast f1.8 primes after >>basketball season, and break out my other lenses for the >>summer shoots, I miss the brighter viewfinder. > >Are you saying that you cant shoot low light with a lens of >f4? I don't know what camera you use but it's no problem with >the D4.As for isolating the background one stop doesn't make >that much difference in the type of shots I take. > I shoot a D3 and I shoot it indoors in gymnasiums and ice arenas. I don't have the ability to use 1/200 exposure....I have to be up near 1/1000 to get good quality sports shots. This really demands the f2.8 a good deal of time, in order to stay out of extremely high ISO's.