70-200mm f/4 L vs 75-300mm f/4-5.6
both no IS, no USM.
what's the main difference between the two? one is a fixed aperture and the other is not. Will the 75-300 f/4-5.6 be fast enough for me to capture motorsports action at sepang track?
Or i really need a f/2.8 for such shots??? however, due to budget constrain, I'm looking at the above 2 lens... pls advise, thank all!