Photography basics: Aperture and shutter speed
The two most important factors to correct exposure in any photograph are shutter speed and aperture.
These two mechanisms are interdependent, so the other must be altered if one is changed.
The lens diaphragm is what the aperture refers to. It is the same as the human eye in ‘auto’ mode. It narrows when there’s a lot of light and widens when dimmed. The f-stops are used to measure the aperture (for example, F1.4, F2.8, F4, f5.6 and f8, f11 or f22).
The diaphragm is wider if the number is smaller. This allows more light into the camera and vice versa. The aperture also affects the depth of field. It determines how much of your image appears in focus.
A narrow aperture (f22), which allows for a shallow depth-of-field, is ideal for portraiture. While a wide aperture (f2.8) allows for a shallow depth of field that only the subject can be in focus.
The second factor that determines exposure is shutter speed. The shutter speed (1/1000th second) determines how much light hits the sensor.
Shutter speed can also freeze action or allow blur in photos. It would help if you froze a mountain biker at 1/500th, 1/1000th sec. However, to blur the water in a rainforest waterfall, you need to take a photo at 1/15th second or slower.
Practice with aperture and shutter speed
Whether your camera is controlled using aperture or shutter speed, the intensity of light hitting the sensor must be the same.
Aperture priority (A) and shutter priority (S or TV) are the camera’s settings to adjust the exposure. In manual mode (M), you have full control. If you change the aperture, you will need to adjust the shutter speed to compensate.
It’s like a sliding scale. The wider the aperture, the faster the shutter speed. The slower your shutter speed, the lower your aperture should be.
Portraiture. You increase your aperture by two stops if your camera reads 1/125th at f5.6.
You can compensate by increasing your shutter speed by 2 stops. This will allow you to maintain correct exposure. The settings should read 1/500th sec at F2.8.
Sport. If your camera reads 1/125th sec at F8 and you want to freeze action in 1/1000th sec, you increase your shutter speed by 3 stops (1/450th, 1/2500th, or 1/1000th). This means that less light is entering your camera.
To compensate, increase the aperture by three stops. This will allow more light to enter your lens. The aperture should read 1/1000th sec at F2.8.