The Human Eye
The human eye looks basically like the illustration. The lens at the left side of the eye focuses light rays onto the retina at the right. The retina converts light rays into electrical impulses that are sent to the brain. Our brain then tells us we are seeing a bit of light.
The cornea is smooth and is clear as glass. It’s strong and it helps shield the rest of the eye from germs, dust, and other harmful matter (along with your eyelids, eye socket, tears, and sclera; the white part of the eye). The cornea is the eye’s outermost lens and it controls the amount of light into the eye. The Cornea behaves like the front of a camera lens. When light strikes the cornea, it bends (or refracts) incoming light onto the lens. The lens refocuses that light onto the retina.
The pupil is the round opening in the center of the eye. The Iris and Pupil act work just like the aperture of a camera. The iris is a muscle which, when contracted, covers all but a small central portion of the lens, allows adjustable control of the quantity of light entering the eye so that the eye can work well in a wide range of viewing conditions, from dim to very bright light.
The Retina is the sensory layer that lines the very back of our eyes and it works similar to digital sensor in your camera. The retina has photoreceptor nerve cells that help change the light rays into electrical impulses and send them through the optic nerve to the brain where an image (of what we see) is finally received and perceived. Because of this reception and perception function, retina is, perhaps, the most important component of our eyes.
How the Eye Works – Animation Video
Just like the human eye, cameras have a lens in front of the sensor to capture light rays. Light rays enter through the lens to the digital sensor; which is sensitive to light.
Eye vs Camera Video
We found a great video from Doodle Science that explains the difference between the eye and the camera. It runs just under 2 minutes.
We have different labels for describing the rays we see. Here are a few basic ones:
- Transmitted Rays: When you look at a stoplight, the top light is red, the middle is yellow, and the bottom light is green. That light is transmitted by putting a light source behind a colored filter.
- Direct Rays: When you look directly into the sun, a camera’s flash unit, or a flashlight you are looking at direct light. The light you see is coming directly from the source.
- Reflected Rays: When you look at anything, you can see that object because direct light is shining on it and being reflected back into your eyes.
- Ambient Light: Think of ambient light as stray light – light rays that are being bounced around from all sorts of sources. If direct or reflected light on the subject is stronger your subject will appear clearer and less hazy.
- Available Light: Available light simply means whatever light is present when not using a flash or other sources of light.