Effect of aperture
The aperture increases or reduces the amount of reflected light from an object which passes through the lens, controlling how much light strikes the film. If the aperture is opened up to increase the amount of light, subjects in front of and behind an in-focus subject will not be focused. That is the range of focus (depth of field) becomes small. If the aperture is stopped down to reduce the amount of light, the depth of field increases. For instance, if you shoot a person against a landscape with the aperture open, the landscape in front of and behind the person will be blurred, making the person appears to rise out of the landscape. By contrast, stopping down the aperture increases the in-focus range.
