What lens? Tips needed :)

[Derrel]

For your first piece of big glass, the 300 f/2.8 is probably the better choice, in terms of ease of transport, ease of use, and general usefulness for sports. You can add a 1.4x teleconverter to a good 300/2.8, and have a decent 420mm f/4 that will be "serviceable", if not as good as the images from a 400/2.8. The weight difference between a fast 400 and a fast 300 is about double--think 7 kg for a 400/2.8, and 3.5 kg for a 300/2.8. Since you shoot a Nikon, you can probably look forward some day to a pro-level body that has a DX crop mode option, which for some uses, is pretty handy. You do not mention which "sports" you are shooting; indoors, a 400 can easily be too long, especially on a 1.5x body. Good, used AF-S 300/2.8 Nikkors can be bought at walk-in retail for around $3,000-$3,500, especially if you are willing to buy the AFS-II model, with the magnesium barrel, which is the one that came out right before the first generation VR model; the magnesium barrel makes it like a pound lighter than many others, and it has very close minimum focus,and superb optics. I have one, and am pretty happy with it. For some types of wildlife, a 500mm f/4 might actually be the better choice than either 400 or 300 2.8 lenses.

 

[MariusF]

For your first piece of big glass, the 300 f/2.8 is probably the better choice, in terms of ease of transport, ease of use, and general usefulness for sports. You can add a 1.4x teleconverter to a good 300/2.8, and have a decent 420mm f/4 that will be "serviceable", if not as good as the images from a 400/2.8. The weight difference between a fast 400 and a fast 300 is about double--think 7 kg for a 400/2.8, and 3.5 kg for a 300/2.8. Since you shoot a Nikon, you can probably look forward some day to a pro-level body that has a DX crop mode option, which for some uses, is pretty handy. You do not mention which "sports" you are shooting; indoors, a 400 can easily be too long, especially on a 1.5x body. Good, used AF-S 300/2.8 Nikkors can be bought at walk-in retail for around $3,000-$3,500, especially if you are willing to buy the AFS-II model, with the magnesium barrel, which is the one that came out right before the first generation VR model; the magnesium barrel makes it like a pound lighter than many others, and it has very close minimum focus,and superb optics. I have one, and am pretty happy with it. For some types of wildlife, a 500mm f/4 might actually be the better choice than either 400 or 300 2.8 lenses.

I like the idea but as you said, will one day upgrade from a DX to FX camera, so the 400mm f2.8 is very tempting since i would like the exstra range of that lens to do some bird shooting.

The sport i shoot is soccer and handball, so the 400 would be a bit to big for the handball on a DX camera but for the soccer i think it would be good. Use a 70-200 f2.8 with a TC1.7 and im still not close on the action sometimes. Only when they are close to me i could use the zoom of the 70-200 but most of the time i miss out since im not close enough. One thing i dont like is the bokeh with the TC on the 70-200 would like the background a bit more out of focus.