Understanding your camera – aperture. The aperture of a camera lens, is the “hole” that the light passes through in order to reach the digital image sensor (or film), this aperture is usually variable, and expressed in f-numbers, as a range by the lens manufacturer, for example f/1.8 – f/22. The numbers are not a physical measurement but rather a ratio between the focal length, and the aperture diameter. The lower the number the larger the “hole” is, allowing more light to pass through the lens to the digital image sensor.
Right that’s the technical stuff out of the way, well almost, so what does this all mean for us as photographers? The aperture controls the amount of light entering the camera, and therefore the exposure, lighter or darker, but for me more importantly is the control of the “depth of field” (another technical term!) The 2 images above were taken with the camera mounted on a tripod, and the focal point set on the foremost object, the 2 glass birds. If you examine the two images above, one is taken at f/2, the “depth of field” at the lowest f-number (or f-stop) is very shallow, and only the foremost object (the 2 glass birds) is in focus. The second image is taken at f/10, the focus point is still on the foremost object, the camera is still on the tripod, but it can immediately be seen that the “depth of field” has increased markedly, the rearmost object is more in focus, and details of the background can be discerned.