When using a camera with manual controls, you have the option to set the aperture. This allows you to determine how much light to allow into your camera, which affects the overall exposure and how deeply focused your picture will be. Setting the aperture on your camera can give your pictures a variety of looks by blurring out the background or keeping it sharp. It also helps determine how bright or dark your pictures will be. Aperture is one of the components of photographic exposure.
Determine if your camera can have the aperture set. SLR (Single Lens Reflex) cameras and some feature heavy compact digital cameras allow you to set the aperture. Look for a command dial on your camera. If it is labeled with an "Av" or "A," it has the ability to set the aperture manually. Some compact digital cameras hide this feature in a menu system.
Understand how the aperture numbering system works. Aperture is given a number value. If the number is small, the aperture ring is open very wide, allowing a lot of light into your camera. If it is a larger number, the aperture ring is not as wide, allowing less light into the camera. An aperture number of f2.8 is a wider opening than an aperture of f8. If all other settings remain constant, a picture taken with the aperture set at f2.8 will be brighter than a picture taken with an aperture of f8.
Adjust the aperture on your camera. Use your camera manual to determine where the aperture setting is on your specific model and brand of camera. Toggle through the numbers, remembering that the lower number will allow more light into the camera. If you are shooting in the fully manual ("M") mode, your shutter speed will stay constant as your set your aperture to different values. Take a few pictures with different aperture values to see how the different settings affect your picture.
Use the "Av" or "A" setting on your camera to select the aperture you wish to use. Use the "Manual" or "M" mode to set both the aperture and shutter speed on your camera.
Setting the aperture on your camera will also effect the depth of focus in your pictures. When using a telephoto lens, a small aperture number will make your background get blurry, so your foreground subject is more defined. This is commonly used in portraiture. Using a wide angle lens with a large aperture number will make your subject matter be in focus form front to back. This is a great option for photographing scenery and landscapes.