« on: February 26, 2013, 04:36:29 PM »
The 5d3 is capable of shooting thin dof and moving kids. The problem might be that it is on the edge of what's impossible AND you have to struggle with the not-canon's-best AF of the 50mm f1.4.
Try the same settings outside and see if more light helps, I'm sure it will.
What you should try, since you say when the kids stop suddenly and it's "Still" oof, that is my experience to, if your AF is set up to respond to fast erratic action, when the subject stops the AF is still in top gear wanting to hit action.
First off, get your AF-start off the shutterbutton and onto the AF-ON button on the back, that way you can, for example, shoot off a few shots of a sequence, track away and shoot off a few more without the AF having to find your subject every time you push and release the shutter.
Then, and this I'm not 100% sure you can do on the 5d3, but I think you can; Select the AE lock button to recall settings and set those settings to fast action with expansion points, case 6 etc. And the AF-ON button to engage "normal" case 1 AF with single point. That way you can just move your thumb 5mm and change the behaviour of the camera COMPLETELY and get all shots focused, even if your kid runs and jumps or suddenly sits down having a sip of his juicebox. Trust me, I know one set up doesn't work with kids, you need to take advantage of EVERYTHING the 5d3 offers, and again, practice, practice, practice.