By choosing how much depth of field to have in your shot, you can focus the viewer’s attention in a specific place. This example shows the same image shot with deep depth of field, and shallow depth of field. Depth of field is controlled by changing the aperture setting on your camera. A camera lens has an iris that you can use to let in more or less light, and you control the size of the hole, or aperture, by changing the aperture setting, measured by f-stop. The larger the aperture, the shallower your depth of field will be, meaning a smaller portion of your image will be in focus, and the smaller the aperture, the deeper your depth of field will be, resulting in more of your image being in focus. To change your aperture, you must have a camera with an aperture priority or manual mode, and on most cameras, Aperture Priority mode is indicated on the mode selector by an A, though Canon cameras use Av. In this mode, you pick the aperture you want, and the camera automatically picks the corresponding shutter speed to yield for good exposure. In a portrait it’s nice to have a shallow depth of field so that the focus is on the person’s face, but shallow depth of field is also handy any time you need a way to separate a subject from a busy background. As you make your aperture smaller, you need to have a longer shutter speed in order to let the same amount of light through to the sensor. A portrait photographer would typically use a wide aperture, giving a shallow depth of field, and a smaller aperture gives a good depth of field.