Help: How to Free-View the Stereo Pairs

Each stereo view consists of two images, one for each eye. Free viewing is the technique that will allow you to direct each of these images separately and simultaneously into each eye. Once that happens, you are said to have "fused" the pair of images into a stereo view.

At the bottom of this page a stereo pair of images is loading with which you can practice. All the stereo pairs shown on this site are in the "cross-eyed" format (my apologies to all the "wall-eyed" people). That means that the first (leftmost) image is for your right eye and the right image is for your left eye. Looking at the pair in a natural, relaxed manner, what you see will be similar to this:

Now cross your eyes, so that the pair of images will double to four, and be somewhat out of focus:

Next, slowly uncross your eyes, and observe with your mind what is happening to the images. At some point, the two pairs of images you are seeing will begin to overlap:

I am indicating with color the region to which you must direct your attention - that area of overlap is where you will fuse the left and right images of the pair. Fusion (yet still without focus) will look like so:

At this stage, your eyes are crossed just the right amount, but your eyes are telling your brain that they are pointing at something about four inches in front of your face - so that's where your eyes are focused. You must dissociate the focus from the pointing, without changing the pointing of your eyes! Simply continue to keep your eyes crossed, keep the blurry images fused, and relax. Examine the blurry details in the fused center image. In a few moments, your brain will direct your eyes to focus on these details without uncrossing. The result is magical, as the image pops into spatial focus:

Please note that free-viewing stereo pairs can be somewhat stressful. If you feel discomfort in the eyes, you should discontinue, and return to the task later. As you use the technique more frequently, your eye musculature will become accustomed, and eye discomfort will be reduced.

If you have trouble, one helpful trick is to use your index finger as a guide for your eyes: hold it up about halfway between your eyes and the screen, and focus your eyes on the fingertip. This helps you to cross your eyes. Notice the nearly merged pair of images in the background, as you move your finger closer or farther from the screen. Once you have the images merged (your finger will probably be 2/3 of the way to your nose), the trick is to allow the focus in your eyes to relax, WITHOUT releasing the physical pointing of your eyes at the fingertip.

If you continue to have trouble with cross-eyed viewing, get ahold of some red/blue 3-d glasses for viewing the anaglyphs.