Pinhole Eye Model




Introduction: Pinhole Eye Model

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Ahoy there, matey! Prepare to get kicked in the eyeballs with this wonder of a vision modification!

The pinhole eye model is a great way to see how squids and octopus see the world, and you'll get a bit of a surprise looking through it. I often preface making this with my students as it revealing "the great lie your eyes tell you." Let's see how!

  • What: Pinhole Eye Model
  • What!?: Oh, just make it
  • Concepts: vision, lenses, focus
  • Materials:
    • Wax Paper
    • Rubber band(s)
    • Two different diameter cardboard tubes (one should be able to fit inside the other)
    • Magnifying lens
    • End for one tube (can make out of cardboard if needed)
  • Tools:
    • X-acto blade
    • Hot glue gun / hot glue

Eye'm excited!

Step 1: Prep Inner Tube

Cut a length of the smaller diameter tube that's a little longer than your wider one. Pull wax paper across one end so it is fairly tight, and secure it with rubber bands. Feel free to cut off extra bits with scissors.

If you can't find tubes, you can do this with just about anything! Two cups with the bottoms cut out work well, too.

Step 2: Make Lens Holder

Okay, so it's not quite a pinhole, but it's the same concept. If you have the end of a mailer tube, that makes things super easy. Pop out a magnifying lens from somewhere, cut a hole large enough, and hot glue it in the end of the cap. If you don't have a cap, make one out of cardboard and glue it on!

It's great to experiment with different lenses with different focal lengths, so making multiple that you can switch out is pretty fly.

Step 3: Scope Your World

Telescope your two tubes, until you see the world projected on your wax paper! It will come in to focus at just one spot perfectly, and that's the focal length of your lens.

Grab different lenses to find other focal lengths and behaviors as well! If you really want to up it up, you can make a large one out of a box that can take camera lenses.

Some science notes:

  • You'll find that your whole world is flipped upside-down, which is how your retina experience it, too! There's a great article here about the process of flipping vision in your brain.
  • Focal lengths are at play here, and are a great subject in optics. Check out the wiki here.
  • This model eye is close to the way octopus and squids see as they adjust the distance and angle of a hard lens at the front of their eye to project differently on to their optic nerve (in our model, the wax paper) to focus on different things. For humans and many terrestrial animals, we have a soft lens that we adjust the shape of with muscles.

Eye hope you enjoy!

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    7 years ago on Introduction

    Great fun for kids! I awoke this morning thinking I wanted to do
    something like this with my son and found your Instructable. Your build
    inspired me to start the prototyping stage. Here is what I have tried so

    It seemed to me a
    spherical shape should have perfect focus if the pinhole is the right
    size. So I thought of found objects that would be spherical that I could

    coat or scratch to make a ground-glass-screen like surface. I considered
    a spherical plastic soda bottle and a spherical vinegar bottle but
    found those got recycled. I didn't have a white plastic ball ideally
    like a large ping-pong ball, so settled on a glass goblet.

    a wash of diluted white paint I could make a screen on half the spherical shape of the goblet.
    I tested it with half and half cream instead so I could clean it off. As far as the pinhole our front door
    used to cast a bright blind spot on the TV so I blocked it off with a
    foam card with a washer glued in the center and panted black. So now
    the front vestibule is somewhat dark and forms a kind of Camera Obscura.
    The final design should be in a black box so the image is shaded enough to be seen.

    The pinhole might be painted on the glass, first in black and then
    decorated like an iris or an actual paper iris could be made as part of
    the box. My peep hole doesn't cast a sharp shadow but if you look out the
    peep hole at the car you can tell what is being projected on the inside
    of the glass "eyeball".

    Uncle Kudzu
    Uncle Kudzu

    7 years ago on Introduction

    Not to be picky, but if it has a lens, it's not a pinhole. That's the cool thing about pinholes; you don't need a lens. (Tomorrow, BTW - the last Sunday in April - is Worldwide Pinhole Photography Day.)

    Wouldn't it be cool if you could get a photo of the projected image from your device? Different effects with different lenses... you could try some filters...

    The Oakland Toy Lab
    The Oakland Toy Lab

    Reply 7 years ago on Introduction

    Hey Uncle Kudzu,

    A great call indeed, our pinhole model is with a lens indeed! Not so pinhole-y, but much of the same principles. Ahoy, and that's great news about Worldwide Pinhole Photography Day! You can make this with just a pinhole in the front, too, but we wanted to add in the lens for another learning point. Thanks for the comment!

    Uncle Kudzu
    Uncle Kudzu

    Reply 7 years ago

    I like the fact that yours telescopes to focus. I might try your project with a pinhole just to see how it behaves.


    7 years ago

    i made it when i was i class 6 with only black char and some glue
    pinhole cameras do not require any type of lenses

    The Oakland Toy Lab
    The Oakland Toy Lab

    Reply 7 years ago on Introduction

    Hey vardaan!

    That is wonderful that you made it when you were young. It's true, you can do the true pinhole experience by just poking a hole in the end of the tube, no lens required! The lens is a bonus that gives one extra learning point. Yay!