Have you ever wondered how humans are able to see in 3D? The three dimensional world is an incredible thing. The way we perceive the world in 3D is no mistake. Our eyes are behind this exciting feat of evolution.
3D vision, otherwise known as stereo vision is probably the most complex feature of our eyes. With two normal functioning eyes, every human should be able to see things in 3D.
But what does that mean exactly? What is 3D? How can I truly know if I see in 3D? Does everyone see in 3D?
Well, these are all excellent questions that have been gnawing at us too! Let’s not waste any more time and jump into understanding what stereo vision is and how we can see in 3D!
What is 3D Vision/Stereo Vision?
Simply put, stereo vision is the ability to perceive depth. Without stereo vision, the world around us would look flat like a picture or a painting. But because we have two eyes that work together, we are able to see objects with depth.
However, not everyone can see in 3D (we’ll get to that a little later) so to be sure that your eyes are working in tandem to bring you depth perception, join us in a little experiment.
Look at an object relatively close to you. It can be anything, a chair, your phone, a book, etc. You will notice that the object has dimension, meaning that it doesn’t look like a photograph of an object.
Now hold up one finger in front of said object and focus your eyes on your finger. You’ll notice that the object has now lost its depth. That’s because your brain is now focusing on the images of your finger being sent, which does appear to be three dimensional.
Here is where it really gets interesting. Next, with your finger still in front of the object, focus on the object. Now it looks like there are two transparent fingers being held in front of the object, which has once again become 3D.
If you got through this experiment without any trouble, congratulations! Your stereo vision is working very well!
How Do We See in 3D?
Now that you know your stereo vision is working, we can delve into figuring out how it works. The explanation to how we see in 3D is actually much simpler than one may think. Your eyes are simply taking two images from slightly different angles, which your brain then combines.
Our eyes are on the front of our face in a relatively side-by-side position, which allows us to see the same image from different angles. Horses, for example have eyes on the opposite sides of their heads, which means that their eyes are constantly looking at different objects.
When our eyes send the slightly different images of the object to the brain, the brain then picks up the slack and combines the two images. The brain matches up the similarities of the images together and then fills in the differences. The result? 3D vision!
Remember when it looked like you were holding up two fingers in front of the object, but in reality it was only one? Well, this is a perfect example of the two images your eyes are taking in. You’ll notice that the finger is seen at a slightly different angle in each eye.
3D movie glasses work on a similar principal, taking the same image at two slightly different angles that come together in one cohesive image when you put on the 3D glasses. This is why when you take the glasses off, the images on screen look like the “two” transparent fingers.
You have the original image and then a second similar image sort of hovering above the action. This is just the original image from a different angle!
Why Do We See in 3D?
The answer to that is simple. We developed stereo vision to survive. The ability to perceive depth is an essential tool in our survival. Our 3D vision allows us to see how far or close things are so that we can protect ourselves from danger.
Could you imagine going for a hike without the ability to see depth? You would risk falling off a cliff or into a ditch or even tripping over rocks and branches. Our ancestors would have been unable to fight or hunt without stereo vision, which would have severely hindered their survival.
In fact, 3D vision is so crucial to survival that the Mars rover is currently equipped with 3D vision. Because signals from Earth can take anywhere between three and 44 minutes to reach the rover, it can be hard to warn the rover when there is danger. For this reason, the rover can perceive depth so that it can avoid crashing into rocks and other dangers.
Unfortunately, not everyone has working stereo vision. Stereo blindness is the inability to see in 3D. This is rare occurrence for people with two eyes. However it always affects those with only one eye.
Whether someone was born with one eye or lost it in an accident, they will always have stereo blindness. Not being able to see an object from two different angles will result in not being able to perceive depth.
This can sometimes affect people with two eyes as well when the eyes are not working together. However, someone with two eyes that don’t work well together can still perceive depth, but not at the same level as two working eyes.
It is suggested that artists (mostly painters) are more likely to have stereo blindness to a certain degree because when painting, you need to ignore your stereo vision. Famous Dutch painter Rembrandt is thought to have been stereo blind because his self-portraits often depicted his eyes to be positioned asymmetrically.
Stereo vision makes the world around us come alive. Without it we wouldn’t be able to see things in 3D and everything would look flat like a painting!