Field of vision demonstration

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This field of vision demonstration is meant to show just how narrow in range the field of vision of the human eye is when it comes to accurately recognizing objects. Performing the test is pretty simple and only requires a deck of playing cards.

To perform the demonstration, do the following:

  1. Shuffle the deck of cards and take one at random and don't look at it.
  2. Stare at a fixed point directly in front you.
  3. Extend your arm out fully and move it as far back behind you as possible so that it's outside of even your peripheral vision.
  4. Flip the card around so that it's facing you.
  5. Without ever moving your eyes from the fixed point, slowly move your arm toward the front of your body while keeping it fully extended.
  6. Before long, the card will be visible in your peripheral vision. If you shake your hand a little, you should be able to see it moving, but, this far in your periphery, you won't be able to make out the number or even the color.
  7. Slowly move the card more toward the front of your body. If you accidentally shift your vision, simply restart the demonstration.
  8. You'll be surprised to discover how, even when the card gets fairly close toward the point you're focusing on, you still can't even tell the color, let alone the suit or number.
  9. As you slowly get closer, the color, suit, and eventually the number or letter of the card will become clear, however, you'll probably be shocked to discover that the card must be very close to dead center before you can finally identify it fully.

This shows us just how narrow our field of vision truly is when it comes to making out detail. We can see motion and large differences between dark and light very far into our periphery, but we can't make out any detail or even color until we get much closer to our focal point.

Another interesting demonstration is to do the test in reverse and see when you stop being able to identify the card:

  1. Draw a random card and hold it up directly in front of you at arm's length.
  2. Slowly move your arm behind you while keeping your eyes fixed on a point directly in front of you.
  3. Notice when you're no longer able to identify the number or letter of the card, then the suit, then the color.
  4. You may be shocked again to discover that, when you perform the test in reverse, you can identify the card much further away from your focal point then when you start from behind you.

This reverse demonstration shows another oddity about our vision: our brain helps fill in the gaps as things leave our focal point. Even though we've shown that our eyes can't determine the color of the card until it gets close to our focal point, if we already know what color it is, our brain will trick us into "seeing" the color well past when we really can.