We’re watching you…
And we’re a little concerned about this myth floating around that your eyes work like little teeny tiny cameras inside your head. According to PhysicsProject-55’s site, “Your eyes are like a wonderful kind of camera.” While it’s true that your eyes and cameras are more similar than say, dogs and basketballs, your eyes are actually much more complex than this popular myth would lead you to believe.
First, let’s talk similarities, because there are some main structures that are comparable in both cameras and eyes.
(Not a camera expert? Don’t sweat it! Check out the image below)
Both your eyes and cameras have lenses. Cameras also have lens elements (the sticky-outy part in front), which can be compared to your cornea. The aperture/focus ring functions like your iris and pupil, and the sensor in a camera can also be compared to your retina.
Now you’re probably wishing you had paid more attention in high school anatomy. “Eye” have another diagram that might help you out!
Are you thinking, “Well, those look pretty similar to me.” You’re right! Superficially, it works out pretty well. And that’s likely why PhysicsProject-55 decided to use this method to explain -to kids- how eyes work.
However, it’s time to be adults (kind of) and “see” the problems with this analogy.
1. For starters, your eyes have about 130 million ‘pixels’ (photoreceptor cells.) For comparison, the fanciest camera I could find online that a professional photographer would use only has 50 million pixels (or 50 ‘megapixels.) That’s a pretty big difference in favor of your eyes.
2. Even more impressive, on a camera sensor, the pixels are evenly spaced over the entire area. In your eyes though, those photoreceptor cells are concentrated in the center. Six million of these photoreceptor cells in your eyes are cones, which see color, and 124 million are rods, which see black and white. The center of the macula (you can go check the diagram, I’ll wait) contains only cone cells, and more than any other area. As you move away from the center of the macula, there’s a mix of cone and rod cells. The further you go, the more rod cells you find, and fewer cells overall. This is the difference in your main field of vision and your peripheral vision. This also means that your eyes have more focusing power than any camera on the market today.
3. There’s also a difference in the way pixels and the photoreceptor cells work. Photographs actually only contain three colors: red, green and blue. Then, the brightness level determines the shade of that color. The brightness level range is 0 (black) to 255 (white). Each pixel represents one color and one brightness level. Because the pixels are so small, after they travel from the sensor to the storage area to make an image, we just see a pretty picture, not millions of tiny boxes. Our photoreceptor cells, however, don’t all function exactly the same way like pixels in a camera. For example, parvocellular cells activate in response to details in color vision. Magnocellular cells are less sensitive to color and respond to movement instead. Visual neurons in your brain also have different jobs, such as noticing decreases in light, or responding to certain colors. This means that these cells and neurons have a wide variety of stimuli that they’re specialized for, not at all like pixels in a grid that only respond to light.
4. One last difference: When you take a picture, every single pixel gets sent from the sensor to the camera’s memory, or storage space, so those pixels become an image that you can save, or share, or sell for millions of dollars, depending on the way those pixels are arranged. Your eyes, however, have so many photoreceptors that your brain can’t keep up. Only the most important information that your retina picks up is actually processed by your visual cortex, about 10%. In this instance, the camera does perform at a higher level. It’s worth keeping in mind though, your eyes developed like this through evolution. By processing only the most important data (what’s right in front of you, or moving in the periphery), your vision is designed to keep you safe.
I don’t get it…
And that’s fine! It’s tricky stuff. Basically, cameras and eyes serve different purposes. A camera is definitely the best choice for capturing still-frame photographs with lots of details, but for high-quality vision, focus, and just plain keeping you alive, your eyes will always come out the winner.
As for this myth?
Sources:
Alshamsi, Ahlam. “How Does the Eye Work like a Camera ?” Physicsproject-55. Accessed September 23, 2015. http://physicsproject-55.wikispaces.com/How+does+the+eye+work+like+a+camera+%3F.
Cicala, Roger. “The Camera Versus the Human Eye.” PetaPixel RSS. November 17, 2012. Accessed September 23, 2015. http://petapixel.com/2012/11/17/the-camera-versus-the-human-eye/.
Lodriguss, Jerry. “How Digital Cameras Work.” Catching the Light. AstroPix, n.d. Accessed September 24, 2015. http://www.astropix.com/HTML/I_ASTROP/HOW.HTM
Ward, Jamie. The Student’s Guide to Cognitive Neuroscience. Hove, East Sussex: Psychology Press, 2010.
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