- The retina in the human eye is similar to the photographic film in a camera. The pupil in the human eye is similar to the aperture (opening) in a camera.
- in a photographic camera, the focal length of the lens is fixed and the distance of the image from the lens changes when the position of the lens is changed. In the human eye, the focal length of the eye lens is changed by the ciliary muscles and the distance of the image from the eye lens is fixed.
- The ciliary muscles adjust the size (the curvature) of the eye lens. The refraction of light is responsible for the working of the eye.