Aperture
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Aperture and shutter speed go hand in hand. It is best to look at them in terms of a triangle, with ISO being the third point. We will review ISO after aperture.
Aperture is related to shutter speed in a similar way. If the aperture is small, you’ll need to have a slower shutter speed to gather enough light to create the appropriate exposure. If the aperture is large, however, you’ll need to have a faster shutter speed to create the same effect.
It’s also important to understand the secondary effects of aperture. A small aperture not only allows less light to reach the image sensor, but it also makes the entire scene appear sharper and more in focus.
This optical phenomenon is called a long depth-of-field. It’s especially useful when you want everything in the viewfinder to be sharp and in focus.
A large aperture has the opposite effect—only your selected subject will be in focus. This phenomenon is referred to as a short depth-of-field.
Portrait photography uses a short depth-of-field extensively because it focuses attention on the subject.
Also, both shutter speeds and apertures have a standard series of settings called “stops.”
Opening the aperture by one stop will double the light that reaches the sensor. Similarly, speeding up the shutter by one stop will cut the light that reaches the sensor in half.
By opening the aperture one stop and speeding up the shutter one stop, you’ll keep the exposure constant.
Opening the aperture by two or three stops and slowing the shutter by two or three stops will have the same effect on exposure—it won’t change. The amount of light that reaches the sensor will remain constant and the pictures will be just as light or dark as before.
What does change, then? Well, the depth-of-field will change, and a moving subject will be either frozen or blurred. Understanding “depth-of-field” will help give you more creative control over your photography and the know-how to take your pictures to an advanced level
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