Stereo Images

Perceptual Illusion

For this project I’ll be discussing stereo images. Stereo images are a type of illusion used to create the feeling of depth so that the viewer sees a 3-dimensional image in a 2-dimensional medium. Stereo images are made up of two images much like our regular vision is made up of two frames (one from each eye). The images differ slightly in angle and this gives viewers the illusion of depth. In other words, stereo images take advantage of the way our eyes perceive depth in the real world.

There are a few different forms of stereo images that create the 3D illusion. The first is when two images are placed next to each other and viewed through lenses. This version has been popular for over a hundred years and is the way virtual reality headsets work today. The second way involves flickering between the two images instead of placing them next to each other, like in these two examples:

http://brainden.com/images/plunge-stereo-image.gif

http://brainden.com/images/stone-gate-stereo.gif

Another form is where both images are placed in one view, requiring special glasses to get the 3D effect.

Mass Effect

The most obvious example of using two images to see depth is of course our own eyesight. The brain takes the information obtained by each eye and presents us with information about the depth of the scene we are viewing.

As I mentioned earlier, virtual reality headsets use stereoscopic images to make users perceive depth in the virtual worlds. An application designed for a VR headset is actually made of two separate views, one for each eye. When viewed without a headset, it looks like two identical views placed next to each other. However, they are not identical- they differ slightly and when viewed through the headset, users see one 3-dimensional image with depth. This example is particularly interesting because being in virtual reality is almost like being in another place. The illusion is used here to imitate reality. I think it’s one of the coolest experiences I’ve ever had, and I believe that this technology has so much potential for the future.

Interestingly, stereo images are also used in medicine to see depth in medical images. For example, stereo images are now used for endoscopies to give doctors depth information about the inside of a patient’s body.

Media Art

In the mid 1800s to 1900s, stereo images were a popular form of photography. The image below shows a picture of Isambard Kingdom Brunel designed for a device called a stereoscope.

Stereo photo of Isambard Kingdom Brunel

Robert Howlett - http://www.photostuff.co.uk/stereo.htm#image2

Interestingly, the View-Masters that many of us played with as children are an example of viewing stereo images.

3D films also take advantage of this illusion. The anaglyph is an image made up of two views: one red and one blue. When viewers see the anaglyph through special 3D glasses (with a red filter for one eye and a blue filter for the other), they can perceive depth in the image.

Example of an Anaglyph

- http://www.photostuff.co.uk/stereo.htm

Although it doesn’t use anaglyphs, James Cameron’s Avatar is a work of art made using stereoscopic cameras. Instead of colored lenses, viewing Avatar requires polarized lenses. Polarized lenses work the same way as the colored lenses however- each eye is shown a slightly different view.

Virtual reality content is another example of stereo images being used to make media. Content ranges from games to short films to music videos. Really any digital content that has before been viewed in 2D can now be viewed in 3 dimensions. Unfortunately, I can’t include any VR content here, but if you have access to a virtual reality headset, I recommend checking out some of the videos at http://www.jauntvr.com/content/. It’s really, really cool.

All of the examples above use stereo images to achieve the illusion of depth. Adding the third dimension to media makes it more life-like.

Reflection

I had no idea that stereo images could be used in medicine. It’s interesting that such an illusion that I’ve usually associated with entertainment can have such an important real-world use.

As for my own digital media, I would love to do more work with virtual reality content (I’m currently doing a VR project for one of my other classes). No matter which form of content I choose to make (videos taken with a stereoscopic camera, 3D games made in a game engine like Unity, etc.), the illusion of depth created by stereo images will be the key to making the media appear so life-like.

In addition, it would be interesting to try to make one of the flickering stereo images I’ve included above.