Despite its relatively simple construction, the human eye is capable of performing a number of astounding tasks that are very difficult for technical equipment to match.
 
Just compare the human eye with a camera. The retina corresponds to light-sensitive film. The cornea, front chamber and lens correspond to the lens on the camera. The iris corresponds to the aperture. Both change in diameter to change the illuminance on the retina or film.
 
The camera and the eye function in very different ways however.. The camera produces a fixed image in the light-sensitive film. The eye provides the brain with a constant stream of data. Even if the eye is focused on a non-moving image the data is still transferred many times a second. By way of simplification, we can say that vision is a result of the combination of the eye as an optical and neural system and a complex and powerful "image processing system" in the brain.
 
Vision is a mixture of innate and learned skills. Known images are recognized faster, for example, than new images. There is still no complete explanation of how the signals and images are processed or how these images are then integrated into our consciousness.