Originally Posted by
GrumpyDiver
Thanks for the additional information, Simon.
Try using AF-C (continuous) mode; as this is the best mode for a subject moving towards and away from a camera. I suspect that your camera has some other fairly high tech facial recognition technology that might work better too.
As for the sheet; I use reflectors for a fair bit of my portraiture and in the situation you were shooting in, I might have tried a piece if white core-plast or foam core plastic at close to ground level to bounce light back at her eyes. On the other hand, that could be rather tricky as you are presenting a young girl with something else to try to explore. White, rather than a silver, reflector pushes out a nice soft light and can easily be much better than flash.
I've read a lot of users suggesting that their camera focus is off, but I've never encountered it and honestly suspect the problem is using the wrong autofocus mode / points rather than a real front focus / back focus issue. I would look at technique before I started blaming the technology.
Sharpening is all about enhancing the areas where light and dark areas of the image meet, so it's not just the edges that show the effect but any areas where this situation occurs. I'm a Photoshop user and 99% of my sharpening is via the unsharp mask method.