A camera adjusts exposure by controlling the amount of light that enters the camera lens and reaches the image sensor. This is achieved through adjusting three key settings: aperture, shutter speed, and ISO sensitivity.
Aperture: The aperture is the opening in the lens that allows light to pass through. By adjusting the size of the aperture, the amount of light entering the camera can be controlled. A larger aperture (small f-stop number) allows more light in, while a smaller aperture (larger f-stop number) lets in less light.
Shutter speed: The shutter speed determines how long the camera's shutter remains open to let light in. A faster shutter speed lets in less light, while a slower shutter speed lets in more light. Changing the shutter speed also affects the motion blur in the image, with faster shutter speeds freezing motion and slower speeds creating motion blur.
ISO sensitivity: ISO sensitivity refers to the camera sensor's sensitivity to light. Increasing the ISO sensitivity makes the sensor more responsive to light, allowing for faster shutter speeds in low-light conditions. However, higher ISO settings can also introduce more noise or graininess in the image.
By adjusting these settings, a camera can achieve the desired exposure for a given scene, balancing the amount of light to create a properly exposed image.