A great photograph depends on a lot of things. A great view, a good camera, good light and of course, aperture settings and shutter speeds. What exactly does the aperture do? It is, basically, an aperture or an opening. The size determines how much light enters the camera through this opening and falls on the image sensor to form the digital photograph. Did too much light get through? Your photograph could be a washout. Was it too little? You’ll get a dark picture.
Apertures come in different sizes – all classified as ‘f’ numbers. Each number lets in double the amount of light as the previous one. The standard is between f/1.8 and f/16. The smaller the aperture, the less light that will be let in. So an f/16 lens will let in half the amount of light as an f/8 lens. The aperture works in conjunction with the shutter as well when it comes to the amount of light let in. The speed at which the shutter opens and shuts is also a factor that determines the amount of light. When it comes to fast-paced action, a fast shutter speed is essential to capture the motion. For a landscape or a posed photograph a slower shutter speed is fine.
A photographer who is extremely particular will adjust both the aperture as well as the shutter speed. A perfect balance between the two could very often bring about that one perfect picture. It needs a trained eye in order to judge perfectly exactly what the settings should be. What he would also take into account is the depth of field, that is, how much of the image remains in focus. In larger apertures, there is just a short range that is in focus, whereas smaller apertures have a much deeper range, going from the foreground close by to way back, deep into the background. It would all depend on the kind of shot to determine what the settings should be. For those of us who do not have the inclination, the understanding or the patience, we can always resort to the automatic setting. It’s simple, the camera does all the work of adjusting for you and you get a good photograph. It might not be a work of art as might a photograph that a true professional photographer might have taken, but most cameras today give you a very acceptable quality.
Why do we need aperture settings at all? The simple, old cameras didn’t have any. If you choose a camera with aperture settings like a telephoto, wide-angle and maximum aperture features, you know that even in an automatic setting, you will get different kinds of pictures, not the same, flat look. It gives you the freedom to take any kind of shot, anywhere, in any light. Otherwise you might find yourself restricted to typical, posed cheesy pictures without too much character or depth.
(original) Aperture
Digital photographs are the result of light hitting the image sensor. Too much light and the photograph will be washed out. Too little light and the photograph will be too dark. The shutter determines how much light enters the camera, and there are two settings which are related to the shutter — aperture and shutter speed.
Aperture is the size of the opening between the lens and the image sensor. Large apertures allow more light to enter the camera than small apertures. Apertures are expressed in ‘f’ numbers — the higher the number the smaller the aperture. Standard lenses are usually rated between f/1.8 and f/16.
Each f-number allows twice as much light to enter the camera as the previous f-number. For example, f/8 produces an exposure which is twice as bright as f/16.
Aperture settings have two basic effects — the amount of light which strikes the image sensor, and the ‘depth of field’. Depth of field refers to the length of the image which is in focus. Large aperture settings have a shallow depth of field — this means that the focus of an image is relatively short which causes foreground and background objects to appear out of focus. Small apertures have a deep depth of field — almost all the objects (foreground and background) will remain in focus.
Aperture is directly related to shutter speed for determining the amount of light that enters a camera. Large apertures combined with fast shutter speeds let in the same amount of light as small apertures combined with slow shutter speeds. Determining which combination is best for a particular situation requires photographic judgment that comes with experience.
To make it easier, most cameras have an automatic setting which will do the calculations for you. Many photographers, however, wish to control aperture and shutter speed for artistic effect.
Since a large aperture can be used in conjunction with a fast shutter speed, this is often a good combination for action shots because the fast shutter speed will ‘freeze’ the motion with a minimum of blurring. Large apertures can also be used for low light conditions where there is very little movement in the scene. In this situation you would combine the large aperture with a slow shutter speed.
Simple point-and-shoot cameras usually have a fixed aperture, and it is only with more expensive models that you have adjustable aperture settings. When choosing a digital camera, one consideration should be the aperture range. There are several ways this can be expressed in the camera specifications: maximum aperture, aperture range, maximum wide-angle and maximum telephoto apertures.
It is more useful to know the aperture range of a particular camera rather than the maximum apertures. A larger range gives you more flexibility in the kinds of shots you can take. A good range for all-purpose photography is from f/1.8 to f/16.
Each lens has its own aperture rating. Telephoto lenses typically have a shallower aperture range than wide-angle lenses because longer lenses need proportionally more light. This is because they are gathering light from a smaller source, so larger apertures are needed to produce f-numbers which are consistent with shorter lenses.
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Quick correction. While an aperture opened to an F stop with a small number lets in more light than a larger one the relationship is related by a square. The authors statement that f16 lets in half as much light as f 8 is wrong. F16 lets in 1/4 as much light as f8. The normal progression of f stops found on most cameras is f1.4, f2, f2.8, f4, f5.6, f8, f11, f16, f22, f32. moving up or down that scale by one position halves or doubles the light. F11 lets in half as much light as f8 and twice as much as f16.
It’s funny, most of the old film based photography books covered this subject pretty well. I guess the new books don’t.