Taking action shots of my kids.

[llubnrut]

Canon 350D, Aperture priority, using 75-300 lense.
When taking action shots of my kids at the park, I am having a lot of focus problems. What focus mode should I have the camera set to? I have tried both AI and AI servo. Is it perhaps the quality/speed of the lense that came with the camera?

Even after ensuring the red light appears on the focus point and the camera beeps I sometimes find their faces are out of focus.

I am looking at upgrading the lense sometime in the future, will this help?

Look forward to some tips and suggestions.

Cheers
Craig

[Marvin]

OK, I am no expert but it would help if we could see some examples of your problem. I find on my camera that if the kids are moving it's better to use continuous servo so that I hold the shutter button half way down and follow the action, then press when I am ready. If your kids move after the beep then they will be out of focus as (on my camera anyway) the beep means it has focused. It may be that your shutter speed is too slow however. If you have a slow lens, then bump up the iso. I think that you need to take faster than 1/500th to freeze the action (but, again I could be wrong and will probably be corrected).