The Aperture is a circular hole within or just behind the lens which restricts light from entering the lens. It is adjustable in size like the Iris of an eye. The larger the diameter of the hole, the more light gets in. So, by changing the size to larger or smaller, strong or weak lighting conditions can be compensated.
Aperture is measured in ‘f-stops’ or ‘f-numbers’. Each change of f-number lets in half or double the light. The wider the aperture, the lower the f-number.
This diagram offers a useful guide as to how the settings of the three elements of the exposure triangle work:
Depth of Field
Changing the aperture also has an effect on how much of the photograph appears sharply focused. The amount that the shot will be in focus is known as ‘Depth of Field’. As we can see from the table below a small aperture will give a larger depth of field; most of the image will be in focus whether near or far away.
Controlling the sharpness of a picture is a great way to direct the viewer’s attention to the focal point of the photograph.
The image on the left was captured at 150th of a second at f/5.0 which resulted in a very shallow depth of field. Because of this the background is out of focus allowing the subject to stand out. The image on the right was captured at 1/50th of a second at f/32 which created a deep depth of field and a sharper background.
Angle of View
“Angle of view” describes how much of the scene in front of the camera will be captured by the camera’s sensor. Defined in degrees, the angle of view can be measured horizontally, vertically or diagonally across an image. The angle of coverage of a lens depends upon its focal length, the longer the focal length the smaller the angle of coverage.
For today’s challenge we experimented with focal length. We photographed a person close up using an 18mm lens and then further away but zooming in at 55cm. This produced the following results:
As you can see, standing close with an 18mm lens, the subject is the focal point of the photograph. Standing further away and using a zoom of 55mm the subject is roughly the same size, but more of the background is encompassed. This also produced a much sharper image. The subject is the same but both photos offer different perspectives. By experimenting with aperture settings and zoom features we can be more creative and achieve much more variation.