Olympus claims that the new AF system is the "world's fastest." It uses the Frequency Acceleration Sensor Technology (for which the adorable acronym is, of course, FAST) that debuted in the PEN E-P3. They've turned up the volume on it, though, pulling data from the chip at 240 fps. In single shot AF mode, it's capable of pulling down 9 FPS at full resolution. The 3D AF tracking system is also equipped for moving subjects. With continuous AF, you can expect somewhere in the neighborhood of 4 FPS.