refocussing speed

Hi I wonder if folks have some knowledge on this. I have been trying out the K10D with my 50mm 1.4 prime with continuous and AF.C on with focus on the centre spot to capture my kids running towards me down a slope. The results are really very good. All the shots are in focus except for one or two. Here's some questions on this:

Does this slow the frame rate down, or does it just depend a) on the speed of the lens and b) what you are asking the lens to do. So my kids running towards me is not quick, but if it was a whippet the camera might struggle.
Is it a case that if the lens does not re-focus in time the camera takes the picture anyway.
If I was to compare the 50mm prime with my £100 Tamron 70-300mm zoom would you expect the refocus speed of the Tamrom to be slower and therefore maybe results could be more unpredictable. Let's say I was shooting a bird of prey at a falconry show, using the Tamron. Would AF.C being on be pointless, assuming I pan correctly and keep on target? So far I have used AF.S for such pictures and get a few good ones to keep.

In AF-C, the shutter fires whether the lens is focused or not, so I presume the frame rate is not slowed down.

AF-C is pointless if you can really keep on target with AF-S.

The 70-300's focusing is slower than the 50's.

thanks, confirming what I thought. with the birds of prey example. probably AF.C might not be a good idea. More importantly if I position myself so that I can pan and have a wide area where the distance between myself and the subject is the same then AF.S might be best, as that same focus will be maintained throughout the continuous shooting. It would seem to me for shooting like that its my best hope for good results.

If the camera and yourself worked perfectly, AF-C should be no worse than AF-S when the distance remains constant. But slight variations in the scene or your aim can make it re-focus (unnecessarily) during the process, so I tend to find AF-C more often annoying than useful.

But that could be down to bad luck or poor skills from me, so you should experiement to find what mode works best for you. There might be times when the bird's distance from you is altering enough to make AF-C worthwhile.

thanks iceblinker, can see your point. should be plenty of wildlife on my next holiday in a weeks time, so will try a few tests. And hopefully post some good results!

I took some pictures a few weeks ago (see-Birds in Flight) and I used AF-C and predective focus point and continious shooting. This was what was advised in a wildlife photo book I was reading and I wanted to try out the approach. I had about a 60% hit rate on acceptable sharpness though I was using the lens wide open (I think) to allow for freeze frame shots.

If you want movement, then panning technique is what counts as critical sharpness is not an issue.

Out of the shots where the bird was flying right at me I had less than 30% success and even had the focus locking on static objects. That is because the focus system finds that situation much harder to deal with.

I have the Tamron 70 to 300 but have not used it for panning shots yet.