Stereo Vision Test: Depth Perception and Dominant Eye

How to use it

1. Choose how you will look. Red-cyan glasses work for most people. Without glasses, you can cross your eyes or look in parallel, as with a Magic Eye picture. On an Owl3D Shift, the test fills the screen.
2. Check the screen size and the distance. The test needs them to turn pixels into seconds of arc. The page guesses both. Correct them if they are wrong.
3. Name the shape. Each picture hides a circle, a square, a triangle or a diamond. You see it only with both eyes together. Choose "No shape" when you see none. Do not guess.
4. Read your result. The test stops at the first wrong answer. Your result is the smallest depth difference you saw, in seconds of arc.

This is a self-check, not a medical test. A low result can come from the glasses, the screen or the way of looking. Only an eye doctor can test your eyes.

How the test works

Each picture is a random-dot stereogram. Both eyes see the same random black and white dots. Inside the shape, the dots of one eye's image are shifted a few pixels to the side. Each eye alone sees only dots. Both eyes together see the shifted dots as a shape that stands in front of the page [1]. You cannot find the shape by looking for edges or colours, so a right answer means your eyes saw depth.

The eight pictures shift the shape by 16, 12, 8, 6, 4, 3, 2 and 1 pixels. The angle of one pixel depends on the screen and on your distance. One pixel of a 100 PPI screen seen from 60 cm is about 87 seconds of arc. The same pixel from 120 cm is about 44. The test shows the finest step your setup can show before you start.

What your result means

Smaller is finer. A seconds-of-arc number is the smallest difference in depth your two eyes could tell apart.

A screen cannot shift less than one pixel. When you pass the last step, your eyes may be finer than the test. Sit farther away to make the steps smaller.

One guess in four is right by chance. Take the test twice. Count the result you reach both times.

Which way of looking?

Red-cyan glasses. Put the red lens on the left eye. Paper 3D glasses are often red-cyan. See anaglyph 3D for how the colours split the two images.

Cross-eyed. The right eye's image is on the left. Hold a finger between your eyes and the screen. Look at the finger until the two pictures make a third one in the middle. Then look at that middle picture.

Parallel. The left eye's image is on the left. Look through the screen, as if at something far behind it. This is the way most Magic Eye pictures are seen. The pictures are small, because parallel viewing works only when the two images are less than about 6 cm apart.

Owl3D Shift. The Owl3D Shift is a 14-inch glasses-free 3D monitor. Turn on SBS Mode in the Owl3D app, then start the test. Each eye sees its own image, with no glasses and no eye tricks [3]. Answer with the buttons or with the keys 1 to 4.

Dominant eye test

Most people use one eye a little more than the other. About 70% of people are right-eye dominant [4]. The dominant eye matters when you aim, shoot a camera, or use one eye at a microscope. Two simple tests find it [4].

1. Make a small opening (Miles test). Stretch both arms out. Put your hands together and leave a small triangle between them.
2. Frame something far away. With both eyes open, look at a far object through the opening, such as a door handle or a light switch.
3. Close one eye, then the other. The eye that still sees the object in the opening is your dominant eye. With the other eye, the object jumps out of the opening.

The Porta test is the same with one finger. Point at a far object with both eyes open, then close each eye in turn [4].

Frequently asked questions

How do I know if I have stereo vision?

Take the test above. If you name the shape in the first pictures, your two eyes see depth. If you see no shape at all, check that the red lens is on the left eye and try again. Then try another way of looking.

What is a normal stereo vision result?

In a study of 188 students, 97% saw depth at 138 seconds of arc and at least 80% at 30 seconds of arc [2]. Clinics use printed tests under set light and distance. This online test depends on your screen, so its number is a guide only.

Why can I not see the shape?

Each eye must see only its own image. Wrong or swapped glasses, a bright room or a tilted head can mix the images. With free viewing, the two pictures must merge into one. Some people have weak or no stereo vision, for example after a squint or a lazy eye in childhood. An eye doctor can tell you more.

Can I test depth perception without glasses?

Yes. Choose cross-eyed or parallel viewing. Both take practice. A glasses-free 3D monitor such as the Owl3D Shift shows each eye its own image directly.

Is my answer saved or sent?

No. The pictures are drawn in your browser and nothing is sent. We count that the test was started and finished, never your answers or your result.

Does stereo vision matter for 3D movies and 3D screens?

Yes. A 3D movie, VR headset or 3D monitor shows each eye its own image. Without stereo vision, the picture looks flat. More on how this works in stereoscopic 3D.