Aperture is the size of the whole in the lens. If the size of the aperture is bigger there is more light exposure, there is more light getting into the lens. When the size of the aperture is smaller there is less light exposure meaning less light is coming in.If the aperture is wider the picture is less focused and there is then a faster shutter speed.A space through which light passes in an optical or photographic instrument. Aperture is measured in F-Stops.