Max Shutter speed
Olympus E-M1 III can shoot continuously at max speed of
15.0 fps and has max shutter speed of
1/8000 sec. E-M1 III also has an electronic shutter which can shoot silently at max speed of
1/32000s. One thing to keep in mind is that electronic shutter may cause rolling shutter / jello effects, and also banding issues under artificial light on your images.
Flash
Unfortunately E-M1 III doesn't have a built-in flash but it has a flash shoe for mounting external flashes.
Focusing
Olympus E-M1 III features both Contrast Detection and Phase Detection autofocus (AF) systems which ensures speed and accuracy of focusing in most situations. The AF system has 121 focus points and 121 of these sensors are of Cross-type. Cross-type sensors locks focus faster and more accurate compared to single type sensors.
Olympus E-M1 III also features
Face detection AF where it intelligently detects the faces in the frame and locks the focus automatically. In addition to the face detect AF, E-M1 III has a more sophisticated feature called
Eye Tracking AF which detects and locks focus to the selected eye of the person in the frame accurately and tracks as the subject moves. Eye tracking AF of Olympus E-M1 III is a perfect feature for shooting portraits and is especially useful when fast lenses are used and the depth of field is very narrow.
Focus Stacking
Macro shooters will love Olympus E-M1 III's Focus Stacking feature. In this mode, E-M1 III automatically composites multiple shots taken at different focal positions using focus bracketing to create a single image with maximum depth of field.