Aperture BasicsAperture is one of the most confusing aspects of photography for new photographers (and some old hands). In truth, aperture does not have to be a confusing aspect of photography. Aperture is an adjustable opening inside the camera lens that works very similar the iris in your eye.
When the aperture opens wide (like your eye dilating), more light is allowed through the lens to expose the film. When the aperture is narrow (like your pupil in bright light), less light reaches the film. Aperture works in conjunction with shutter speed and film speed to determine the total amount of light that reaches the film. Aperture size also affects depth of field.
Measuring Aperture
.Aperture is measured using F-Stops. F-Stop numbers represent a fractional formula representation of the amount of light allowed to pass through the aperture. In simpler terms, F-Stop numbers get bigger as the aperture gets smaller, just like shutter speed numbers get bigger as the time the shutter is open gets smaller. Each increasing F-Stop number roughly represents a halving of the light reaching the film.
F-Stop Relationship to Light
Big F-Stop Number = More Light Needed
Little F-Stop Number = Less Light Needed
While there is actually a huge range of F-Stops (aperture sizes) possible, depending on your lens, there is a common ground middle range that most consumer lenses are capable of operating within.
Common F-Stop Values
f/4 f/5.6 f/8 f/11 f16
Setting Aperture
Aperture is set on cameras by turning a specified dial on the camera body. In older, fully manual cameras, this is a dial on the camera lens that is marked with F-Stop numbers. In newer cameras the aperture is generally displayed on an LCD screen while the photographer turns a small wheel near the shutter release button to adjust the setting. The exact placement of the wheel will vary from camera to camera. On point and shoot cameras, there may not be a control to select specific aperture or F-Stops. Instead, you may need to understand your camera's preprogrammed modes to obtain the desired aperture. Many SLR cameras also have these preprogrammed modes as well as a few additional modes of fine control.
image from www.youcanclick.com Aperture in Preprogrammed Camera Modes - Basic
.Almost all automatic cameras today have some sort of preprogrammed shooting modes. These are designed for specific situations such as action, landscapes, and portraits. If you know what these modes change about your camera settings you can use them to your advantage in many more situations than just the intended ones
Macro
Macro mode is an automatic setting mode where the camera is predisposed to use the large aperture to compensate for the DOF compression of close-up shooting. In this mode you can not set the exact aperture you want but you can lessen your chances of an out of focus close up subject by using this mode.
Landscape
Landscape mode is basically a large DOF mode. Landscape is programmed to give the smallest aperture (largest F-Stop) possible in order to ensure a large depth of field. This means that the shutter speed will be slower. If your camera does not allow Manual or Av mode and you are wanting to shoot a subject where the background is in focus, try the Landscape setting.
Portrait
Portrait mode uses a large aperture to create a small DOF. Portrait is programmed to have a shallow depth of field (large aperture/small F-Stop) and use a slow film speed in order to throw the background out of focus and obtain a very fine film grain. Use this setting anytime you want a blurry background.
Aperture in Preprogrammed Camera Modes - Advanced
Manual
Manual setting is marked "M" on newer cameras and is, in effect, the only setting on manual cameras. Manual mode means that you are fully in charge of the settings of your camera. If you set the aperture/F-Stop while in M mode, you will need to make an adjustment to shutter speed yourself in order to maintain a correct exposure. Use your camera's light meter to ensure the values are in balance.
Aperture Priority
The setting on your camera marked "Av" is called Aperture Priority mode. This means that if you use Av mode and set the aperture/F-Stop, the camera will adjust your shutter speed value to maintain a correct exposure.
Program
Program mode is marked by a "P" on the few cameras that have this option. In program mode, your camera responds to some preset conditions you programed through the menu. Generally, this mode allows you to set either the shutter speed or the aperture while the camera adjusts the other setting to maintain proper exposure.
