Samsung Galaxy NX500 Camera User Manual (en)

Concepts in Photography
The aperture is one of the three factors that determine the exposure. The 
aperture housing contains thin, metal plates that open and close to let 
light through the aperture and into the camera. The size of the aperture 
is related to the amount of light: a larger aperture allows more light and a 
smaller aperture allows less light.
Aperture sizes
Minimum aperture
Medium aperture
Maximum aperture
Aperture opened slightly
Aperture opened wide
The size of the aperture is indicated by a value known as the “F-number“. 
The f-number represents the focal length divided by the diameter of the 
lens. For example, if a lens with a 50 mm focal length has an f-number of 
F2, the diameter of the aperture is 25 mm. (50 mm/25 mm = F2)  
The smaller the f-number, the greater the size of the aperture.
The relative size of the opening in the aperture is indicated by the 
Exposure Value (EV). Increasing the Exposure Value (+1 EV) means the 
amount of light doubles. Decreasing the Exposure Value (-1 EV) means 
the amount of light halves. You can also use the exposure compensation 
feature to fine-tune the amount of light by subdividing exposure values 
into 1/2, 1/3 EV, and so on.
+1 EV
-1 EV
Exposure Value Steps