Aperture
The aperture is the size of the opening in the lens, which controls how much light enters the lens. The aperture is measured using ‘f-stops’, and can be adjusted by changing the ‘f-number’. A large aperture is indicated by a small f-number (f/2.8) , and lets more light pass through. A small aperture corresponds to a large f-number (f/16), and allows less light to pass through.
The size of the aperture also helps control the depth of field, or the range of distance in an image that appears focused or sharp. A small aperture (large f-number) creates a large depth-of-field, meaning an overall sharper image in which the foreground and the background are in focus. A large aperture (small f-number) creates a shallow depth-of-field, in which the subject of the image is in sharp focus and the background is soft and blurred.
Chart of f-stop progressions.
Shutter Speed
The shutter speed is the amount of time the camera’s shutter remains open when taking a picture. Shutter speed is measured in seconds and displayed in fractions of a second, e.g. 1/4s, 1/60s, 1/250s, 1/500s, etc. The length of time the shutter is open when taking a photograph determines the amount of exposure in the image. The longer the shutter remains open, more light is able to pass through to the image sensor.
Adjust the shutter speed depending on the image being captured. To freeze the motion of a moving subject, select a fast shutter speed (1/1000s, for example). Use fast shutter speeds when shooting sports events, performances and wildlife.
Example of freezing motion using a fast shutter speed.
To blur the motion of a subject, select a slow shutter speed (1/60s, for example). Slower shutter speeds are useful when capturing the motion of waves, rushing water, and light trails from car headlights and tail lights. Be sure to use a tripod when shooting with slow shutter speeds to keep the camera steady while the shutter is open. You don’t want to ruin your photo due to camera shake.
Example of long exposure, slow shutter speed in capturing blurred motion.
ISO
ISO is the measure of the camera’s sensitivity to light. ISO sensitivity controls the amount of light necessary for the image sensor to achieve a certain exposure. The ISO is indicated numerically from ISO 100 representing low sensitivity, to ISO 6400 representing high sensitivity. Light sensitivity decreases as the ISO number decreases, and vice versa. Setting the camera to a high ISO allows the sensor to capture images in low-light settings without having to use a flash. However, shooting in dark environments using a high ISO creates grain or “noise” in the photographs. Low ISO numbers (ISO 100 or ISO 200, for example) should be used when shooting outside on a sunny day. The camera sensor does not have to be very sensitive in these conditions because there is a large amount of available light that will reach the sensor during exposure. This results in clear, high quality images with minimal grain. Be careful not to set the ISO too high in bright environments to avoid over-exposing and washing out the images.
ISO scale.