Samsung Galaxy NX500 Camera User Manual (en)

My Camera > 
Shooting modes
 Aperture Priority mode
In Aperture Priority mode, the camera automatically calculates shutter 
speed according to the aperture value you choose.
You can adjust the depth of field (DOF) by changing the aperture value. 
This mode is useful for taking portraits, flowers, or landscape shots.
Large Depth of Field
Small Depth of Field
Rotate the mode dial to A.
Scroll command dial 1 or command dial 2 to adjust the 
aperture value.
You can also assign other functions to command dials 1 and 2. 
(p. 177)
You can also adjust the aperture value by pressing [f], moving to 
the aperture value, and then scrolling command dial 1 or dragging 
your finger on the screen.
Set the desired options.
Half-press [Shutter] to focus, and then press [Shutter] to 
capture the photo.
In low-light settings, you may need to increase the ISO sensitivity to prevent 
blurred photos.
To set the minimum shutter speed, in Shooting mode, press [m] 
Minimum Shutter Speed 
 an option.