Learn To Freeview Cross

Learning to "freeview" an image by crossing your eyes is actually quite easy.

("Freeview" = see a stereo image as 3D without using a viewer)

When starting out, pick a simple image to begin with, not anything visually complex. Ideally, you should choose an image with a at least one small patch of different colour. I've found that a bright image with a dark patch is easier to "verge" on than a dark image with a bright patch. Here's the image that I'm using in my examples below.

Start out with smaller images, and work your way up to a full screen like I've mocked up in the images below. You might also find it easier to have a black border around the images (including a black area between them).

Hold up one finger and look with both eyes. You'll see two images of your finger:

It's hard to stay aware of both images of your finger, your brain is used to filtering this out. It can help to wiggle your finger a little, so you can be aware of it, but keep looking at that monitor.

Got it?

Now try the opposite - look at your finger:

At first, just try to learn to be aware of the background. When you think you've got it a little, adjust the distance of your finger so that the two images of the stereo pair line up with each other while you're still looking at your finger.

Re-wording that to be clear: You should be seeing two copies of the background, just like you had two copies of your finger before. You've moved your finger closer or further from your eyes until the two halves of the stereo image have lined up. You can line up your finger more easily by looking at the image and getting the two images of your finger to cover the same part of the image.

The last little step is not as hard as the others, but it takes a while to get without losing it halfway. That last step is to transfer your focus to the image behind, without just looking at the monitor. You want to keep the doubled image in view, and get it in focus. You should be able to "snap" or "lock" in on the image, and remove your finger.

If you can keep your attention on the stereo image but you're having trouble focussing on it, it can help to move your head backwards and forwards a little.

When you get it, the stereo image should snap into focus, and you'll notice that it's 3D now!

This animation shows what it should all look like:

With time, you should learn not to need your finger, and you can learn to find the focus more easily too.

Good luck!