The Human Eye as Compared to a Camera
Do you remember before the days of digital cameras? When we actually had to load a roll of film into a very expensive camera and were allowed to take either 24 or 36 pictures on a single role?
Let's compare the basic principles on how that camera worked as compared to how the human eye functions.
First a couple similarities; both a camera and our eyes have a lens. Both a camera and our eye have an aperture device. Both receive light and maintain a method of capturing that light. And both have a function to interpret that light into an image.
For starters lets look at the lens system. A camera has a lens on the front surface that (on some models) can be interchanged for varying range of focus. Our eyes work on a two lens system. The first lens, the cornea is on the outer surface of the eye and can be compared with a cameras lens.
In order to adjust focus on a camera, the lens tele-photos meaning it extends in or out in a dynamic function. In the eye, we have a crystalline lens that also adjusts shape so we can adjust our focus in and out.
To adjust light, the camera has aperture settings. While many cameras will do this automatically, true photographers point their camera towards a grey card and get a light reading so they can adjust the aperture setting. Fortunately for us, our eyes adjust aperture automatically. The opening is called the pupil, which is actually just a space. The pupil is not a physical part of the eye, rather a reference name for that round dark area between the iris.
The iris is the colored portion of the eye and is responsible for controlling how much light enters the eye.
In both a camera and our eyes, the light and image are inverted by the time they reach the receiving mechanism. In a camera, that is the film, while in the eye that is the retina.
So here is where things get a little different, on a camera light is allowed through the lens system for a portion of a second so the image can be burned on to the film. The film is then processed and a static image is saved as a negative.
When light enters the human eye, it is received by the retina, which is an extension of our brains. Neurons transmit that image to the back portion of the brain in an amazing process and we perceive an image.