Aperture

Introducing Aperture = Depth of Field

The depth of field is the area of sharp focus extending in front of and behind the point you actually focus the lens on. A large lens opening f/2.8, gives you less depth of field than a small opening f/16 or larger f/number.

Area of sharpness

Set on AV, F5.6 Stop, 1/60 s, ISO 100, Taken outside
Shallow Depth of Field

Set on AV, F6 Stop, 1/160 s, ISO 100, Taken Outside
Shallow Depth of Field

Set on A, F6 Stop, 1/60 s, ISO 100 Taken at the park
Deep Depth Of Field, Self-Directed Time

Set on A, F4 Stop, 1/40 s, IS0 100, Taken at park

Shallow Depth Of Field, Self- Directed time

Lewis Hine

                                                Girl worker in Carolina cotton mill
                                                                            1908