Samsung Galaxy NX500 Camera User Manual (en)

Shooting Functions > 
AF mode
Single AF
Single AF is appropriate for shooting a still subject. When you press 
[Shutter] halfway, the focus fixes in the focus area. The area turns green 
when the focus is achieved.
Continuous AF
While you press [Shutter] halfway, the camera continues to focus 
automatically. This mode is recommended for shooting action.
Depending on the type of lens, auto focus results may differ when you 
capture photos continuously using Continuous AF. Use an optional lens for 
smooth auto focus operation. Select an optional lenses from the following:
SAMSUNG 16-50mm F2-2.8 S ED OIS
SAMSUNG 16-50mm F3.5-5.6 Power Zoom ED OIS
NX 50-150mm F2.8 S ED OIS
When using Continuous AF and Multi AF, press [o] to resize or move the 
focus area while shooting. Use command dial 2 to move the focus area. Scroll 
command dial 1 to resize the focus area. When you press [Shutter] halfway, 
the camera focuses only on the set focus area. The focus area moves with the 
subject after the focus is set correctly.