Differences Between the Eye & a Pin Hole Camera

People often compare eyes to cameras, as both have the ability to capture light and transform that light into discernible imagery. One of the most basic types of cameras is the pin hole variety, which uses a tiny hole to channel light into a box and then displays that light as an inverted image on its back surface, where film is stretched out. Although eyes and pin hole cameras perform similar functions, they also have several, significant differences.

Shutter

• Both eyes and pin hole cameras rely on shutters, or movable structures that can let in light when open and bock light out when closed. However, while eyes are able to keep their shutters, or eyelids, open for hours-on-end --- with the exception of blinking --- and continuously provide current imagery --- both moving and still --- as they receive light, pin hole cameras have a much shorter functional time span and can only produce still images of particular moments. If you leave the shutter open for more than a few seconds, the camera's box will become flooded with so much light that it will be unable to process it. In terms of composition, the University of Wisconsin notes that eyelids consist of thin layers of skin and are controlled by muscles. In comparison, a pin hole camera's shutter typically consists of paper, cardboard or some other flat, opaque item and relies on a hinge for movement, which can be as simple as a piece of tape.

Lens

• According to the University of Edinburgh School of Informatics, the eye's lens is responsible for focusing light onto the retina, where photo receptors then absorb and convert the light into electrical nerve impulses for the brain. The eye lens uses contracting muscles to adjust the amount of light the retina receives, which is why your sight will eventually grow accustomed to very bright or very dark environments. In contrast, the lens, or light-gathering component, of a pin hole camera is a stationary box, which can only focus light in a single configuration. Also, instead of directing light on to cellular photo receptors that send the light for processing in the brain, the lens of pin hole camera directs light on to film or photographic paper.

Cornea

• The cornea is a transparent, convex layer of tissue that covers the front outer surface of the eye. It allows light to enter into the eye's lens, while simultaneously protecting it from outside debris. Although more sophisticated types of cameras have cornea-like outer glass coverings at their apertures, or openings, pin hole cameras have no such coverings. Instead, their apertures are unsealed, and their internal elements are exposed to the outside air when the shutter goes up.