What is Aperture?

Aperture is another element of photography I must get my head around! Test images will follow shortly.

What Is Aperture?

The main function of a camera lens is to collect light. The aperture of a lens is the diameter of the lens opening and is usually controlled by an iris. The larger the diameter of the aperture, the more light reaches the film / image sensor.

Aperture is expressed as F-stop, e.g. F2.8 or f/2.8. The smaller the F-stop number (or f/value), the larger the lens opening (aperture).

In practice, unless you are dealing with a fixed-aperture lens (many simple point-and-shoot cameras have only one fixed aperture), the aperture of a lens is usually expressed as a range of fstops.

When you read the specifications of a camera, the aperture may be expressed in a number of different ways, the following three being the most common:

• Maximum Aperture:

Max. Aperture

F2.8

This simply states that the maximum aperture for the lens is F2.8.

• Aperture Range:

Aperture Range

F2.8-F8.0

This states the max. and min. aperture, the assumption being that there are standard increments between them.

• Maximum Wide-Angle and Telephoto Apertures:

Aperture

F2.8-3.5 or F2.8(W)-F3.5(T)

This gives the max. aperture for the wide-angle (F2.8) and telephoto (F3.5) focal lengths of a zoom lens.

It is usually not too difficult to figure out that a stated range deals with maximum apertures and not max and min apertures: the mimimum aperture should be quite small at F8, F11, F16 or F22.

I shall follow this write up very soon with an image taking excercise to demonstrate the aperture settings by altering the FStop from small to large.