NX500 - Disappointed by AF performance

Raw Jaw wrote:

Thank goodness it was the camera and not you.

No need to be offended?

I consider myself a beginner, and don't know the technical details. You suggested that using Continuous AF was the big mistake, and that I should read the handbook. The handbook did not clarify why Cont AF performs so much worse (this, BTW, is just speculation, we don't know whether single-AF would have been the solution, but of course I'll try).

So, all I did was ask, and I do it again: Can you explain to me why Cont AF performs so much worse?

I mean, some scenes didn't change much overall (like blowing out the candles), but still a lot happened. So I just took one picture after the other. Approx. 30% are utter rubbish, i.e. focussed on something completely different than the AF-square or is totally blurred (see the attached example, before releasing the shutter, there was a green square just covering the face of the central child). The next two images focussed on the red box in the background (at least something), and the next image was nicely focussed on the face of the girl (the way I wanted it, and the way I would have thought because indicated by the green square on the face).

Honestly, how can I avoid this? I take a series of pictures under virtually identical conditions, and some shots go wrong by so much?

If I can do better, then I really want to. But for this I need to understand what went wrong.

Best wishes,

Andre