Samsung NX1000 User Manual page 47

Manual mode lets you adjust the shutter speed and aperture value
manually. In this mode, you can fully control the exposure of your
photos.
This mode is useful in controlled shooting environments, such as a
studio, or when it is necessary to fine-tune camera settings. The Manual
mode is also recommended for shooting night scenes or fireworks.
When you adjust the aperture value or shutter speed, the exposure
changes according to the settings, so the display may darken. With this
function on, the brightness of the display is constant regardless of the
settings, so you can better frame your shot.
Use a bulb to shoot night scenes or the night sky. While you are
pressing [Shutter], the shutter is left open so you can create moving
light effects.