Alister Ling and I setup about 20m apart on the 142 Street bridge over the MacKinnon Ravine to shoot a time-lapse movie of the full moon rising. We synchronized our cameras so we could select a matching pair of frames to produce the free-fuse stereo pair above. If the image is too wide for your monitor, click here (or the image) to open it as a resizable image.

Concentrate on pair of images, tilting your head until the two images are level with each other. Place your index finger at the border between the two images with your fingertip at the bottom of the images. Now keep your attention on the fingertip as you very slowly move it from the screen toward your nose. Notice what's happening to the two images on the screen: they're moving together as you cross your eyes to track the fingertip. Notice that they are also going out of focus as your eye lenses adjust to keep your fingertip in focus. When your finger is about 20 cm from your nose (this will vary quite a bit based on your interocular separation and the distance from your eyes to the screen), the two blurry images in the background will merge with the left image overlapping the right one. At this point, you'll perceive three images: the left, the fused combination of the left and right, and the right.

Fuse the images by focusing on your fingertip and hold your attention on the fingertip for about 10 seconds. Be sure the fingertip is below the fused image, not overlapping it. Now focus your attention on that fused image. As you shift your attention, the lenses of your eyes will refocus on the screen while remaining crossed correctly for viewing the finger. You should now see the fused image in 3-D. It is possible to look around the fused image with the eyes crossed.

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Click the thumbnail below to see Luca's time-lapse movie (3.7 MB).

Click the thumbnail below to see Luca's composite image of the event.