How does back focusing work?

[Thommo]

I shot a heap of rugby today and my shots arent looking all taht sharp.

I was actually shooting for a guy who sells prints via his website, and he didnt use alot of my stuff as it wasnt sharp enough. ( the focus was slightly off in alot of them). Im pretty sure this is just me and inexperiance but is it possible for back focus to only occur in AF-C?

Does anyone have any pointers for what autofocus settings to use for sports like rugby? Everyone there today was using canon gear so they had no idea!

Looks like tommorrow im going to be shooting with his 1dii and 300 anyway as i just dont have the reach with d700 and 70-200.

[shakey]

Not sure about D700 modes, but on D70 AF-C will let shutter be released withouut focus acquistion. On D300 there are further AF-C options which will modify shutter release, depending upon whether focus is acquired or not.

In addition there is AF dynamic tracking which maximises the likliehood that your subject will be in focus in AF-C mode. Again I'm not sure about the D700 options, but the D70 has a fairly good system, and I'm still working out the D300.

If you can get well focussed shots in AF-S mode then I'm doubtful that any poorly focussed shots in AF-C are due to "back focussing" and are most likely due to the inherent nature of the AF-C mode.

Can't tell you mode choice on a D700 for action football shots, but for D70 mine would be AF-C, dynamic area mode

For D300 - AF-C, focus priority, dynamic area 21 points

Interested to hear other points of view (especially for D300...since it's fairly new for me)