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What is it?

The aperture refers to the circular hole in a lens that allows light through. A camera’s lens is designed to allow the size of the aperture to change so that the photographer can control how much light is being allowed through the lens. 

Where is it?

The mechanism that allows the aperture to vary in size is known as an “iris diaphragm”. The iris diaphragm can change the aperture size as it is actually composed of a series of interlocking blades that can fold in each other or expand out.

Aperture and Depth of Field

In the Exposure section, it is mentioned that different aperture and shutter speed combinations can be used to achieve the same exposure. The main reason why photographers would want to set different aperture sizes to shoot with is because the aperture size is the factor that has the most effect on the depth of field in a photograph. ‘Depth of Field’ refers to the distance (depth) between the nearest and farthest objects that appear in acceptably sharp focus in a photograph. Creative use of aperture settings can help control the depth of field in a photograph.

How is it Measured?

Aperture is measured in a unit known as an ‘F-stop’ or ‘F-number’. It is not necessary to understand how F-stop is calculated, but what is important for you to know are two key things:

  1. The F-stop indicates how much light is being allowed into the camera regardless of the lens used.
  2. The F-stop is an inversely proportional unit of measurement. That is, the smaller the F-stop number (F4), the larger the aperture (more light/larger opening); and bigger the F-stop number (F25), the smaller the aperture is (less light/smaller opening).


The F4 and F25 aperture settings listed on point 2 under the ‘How is it Measured’ section, are the lowest and highest F-stop numbers on the Nikon D7000.