A photographer's setting typically includes the APERTURE, AUTO, and f-stop settings. The APERTURE is the size of the opening in the lens that allows light to pass through, and is measured in f-stops. AUTO mode allows the camera to automatically adjust the settings for the best exposure. F-stop is a measurement of the size of the APERTURE, and is usually expressed as a fraction. Together, these three settings allow photographers to control the amount of light entering the camera, and thus the exposure of the image.