The aperture of the lens
The shutter speed
The ISO setting-how sensitive you want the camera sensor to be
IT will require two parts to answer your question as it's phrased. The camera's shutter controls the time that light falls on the film, so controls the duration of exposure, and the lens aperture controls the brightness of the light falling on the film. The two functions are used together to get the desired effect.
The aperature setting controls that amount of light that will fall on the image. The aperature is a whole formed by the shutter itself, the aperature setting (also known as "F-stops" control how large the opening will be, thus the amount of light that touches the image. The larger the number (for example, f20) the less light will hit the image, the smaller the number (for example f2.8) the more light will enter the image.
The shutter controls this by quickly opening and then closing to let light in for only a brief moment.
the ISO setting in your camera controls the shutter speed therefore increasing or reducing the amount of light captured by the film/photocell
SHUTTER in Camera controls the amount and time of light that the Sensor will exposed to.
It controls the amount of light that reaches the film.
The same as the irises of your eyes, it controls the amount of light that passes through the aperture.
The functional opening is the aperture, the opening that controls the amount of light that hits the photosensitive surface. You may have a camera with interchangeable lenses that screw into and out of the camera's body. The opening into which the lens is screwed is not the aperture.
Shutter speed, aperture, and ISO are the three main factors that control exposure in photography. Shutter speed determines how long the sensor is exposed to light, aperture controls the amount of light entering the camera, and ISO adjusts the camera's sensitivity to light.
The Shutter and the Aperture are the two controls the Shutter is used to control how long the Film is exposed for and Aperture is used to control how much light is let in
Iris controls the amount of light entering into the eye.
the diaphragm controls the amount of light entering the microscope
The lens is made of glass and plastic (or groups of glass elements) and focuses light passing through it on film to reproduce an image. The diaphragm is an opening or aperture that controls the amount of light entering the camera from the lens and so limits the film's exposure to light.
the iris controls the amount of light by limiting the volume of light admitted through the iris.
The human eye can be compared to a photographic camera because the pupil of the eye and the shutter on a camera, is what controls the amount of light let in. As for differences, a human eye is alive while a camera is an inanimate object invented by man.