Authentic world

 There are two primary exposure settings on adjustable cameras that control the amount of light that reaches the film or matrix and exposes it. There are shutter speed and lens opening. 

•  The shutter speed controls the length of time the film or matrix is exposed to light and is expressed in numbers such as 30,60,125,etc. These numbers represent fractions of a second (e.g., 125=1/125 of a second). 
•  The B setting on the shutter speed scale means the shutter will stay open as long as you press the shutter release. Use the B setting for time exposures. 
•  The size of the lens opening on your camera (indicated by f-numbers) is the other factor that controls the amount of light that reaches the matrix. 
•  The smallest f-number on a lens refers to the biggest lens opening and the largest f-number refers to the smallest lens opening. 
•  When you change from one lens opening to the next nearest number, you're adjusting the lens by 1 stop (except from the maximum lens opening to the next smaller opening on some lenses). 

Lens opening f-number	Shutter speed	/\ | | more light or expo- sure |
4	1/30
5,6	1/60
8	1/125
11	1/250
16	1/500

 "Equivalent Exposures (the corresponding pairs are united by colors) " are many combinations of shutter speed and lens opening that allow the same amount of light to reach the matrix or film for proper exposure. This lets you use a smaller lens opening to increase depth of field or a higer shutter to stop actions: e.g., as the setting in one column is increased, the setting in the other column must be decreased to maintain the same exposure for the lighting conditions in the scene you want to photograph.