In our last session, we learned how ISO Sensitivity can help in controlling the light that exposes the sensor to produce an image. Today we will learn about the second factor that can control the light, that is Aperture.
What is Aperture?
The aperture is the opening found in your camera lens. The one through which light passes up-to your sensor. If you look closely at the lens of your camera, you will find the round or ring-like metal blades. These blades open and close: it opens to widen the opening, and it closes if you want the opening to narrow down.
Understanding The Aperture
A wider aperture (or lower f-number) means more light will go through the lens, simply because the opening is larger. A narrower aperture (or higher f-number) will allow less light to reach the sensor.
Aperture is measured in f-stops (or stops) usually ranging from 1.2 to 32. In fact, each time you double the area of that opening, you double the amount of light or increase the exposure by one stop. The aperture setting is determined by several f-stop values. The usual numerical values for the f-stop are 1.4, 1.8, 2.0., 2.8, 3.6, 4, 5.6, 8, 11, 16 and 22.
Aperture and Depth of Field
Aperture plays two important roles in photography. First, it limits the amount of light that passes through the lens so you get a properly exposed image.
Second, it controls the depth of field (which is the range in the image that is in focus). The smaller the aperture size, the wider your depth of field — a deeper portion of your photo will be in focus. Another way to explain Depth of Field is the area of sharpness in front of and behind the subject you’re focused on.
Why use a narrow aperture?
You might wonder why we would ever want less light to reach the sensor. The answer to that in the majority of time is that we want a larger depth of field. The depth of field is a byproduct of the aperture. Narrower apertures (higher f-numbers) give a greater depth of field, allowing more of a scene to be in focus (think landscapes or a wider range of subject distances). Wider apertures (lower f-numbers) create a narrow depth of field, which can help isolate a subject and is one of the greatest compositional tools at your disposal (think portraiture).