If you plan build a stereoscope, you’ll want something to look at! I suggest starting with this step. With a stereograph in hand, you can better test and tweak your stereoscope during the building process.
There are several options for creating your stereograph. There are thousands of original stereograph images available online, including collections from the National Museum of American History, the Library of Congress, and the New York Public Library. You can print one of these out to the correct size and adhere it to a backing board to hold it firm. Here are the measurements I used for the pictures on my card:
If you would like to make your own original stereograph, you will use these same measurements when printing your photos. There are two options for taking the stereograph pictures. First, you can take the two photos by holding your camera steady, shifting your weight to your left foot, taking a picture, then shifting your weight to the right foot and taking a second photo. This approach will simulate the view from your left and right eye. For a more precise stereograph, take advantage of a smartphone app. I have no particular affiliation with the product, but did try and like “3DHolicCam” (available for iPhones).
Now that you have a stereograph, let’s make something to view it with.
Reading glasses (ideally of a high magnification. I used a pair with 2.5x)
Scissors and/or utility knife (helpful for cutting out the eye pieces)
Hot glue gun
Black construction paper
I began with a tutorial by Make: magazine to create the lens piece for my stereoscope. The linked article explains how to repurpose reading glasses into a simple stereoscopic viewer. I didn’t have all the suggested tools; where the author called for drilling and screwing the lenses, I instead glued the pieces of the glasses to an angled piece of cardboard. My final stereoscope worked just fine with this adjustment.
After making the lenses, I tested them with my stereograph. I held the lenses up to my eyes with one hand and the stereograph out in front of me with the other. When you try this, looking through the lenses should feel like crossing your eyes, and they should force the two images to converge on one another. You may need to move the card closer or further away from your face to get the images to overlap and focus. With my first attempt at the lenses, I found that the pictures were not overlapping at all. So, I separated the glasses pieces and tried a different angle on the cardboard connecting them.
Even after this tweak, I still didn’t achieve perfect stereopsis. The images partially converged, but my eyes took in too much of the periphery around the stereograph and I found it difficult to get the illusion to work. To resolve the issue, I built a simple cardboard housing, modeled on a stereoscope we have at the museum.
Here’s how you can do the same:
Cut cardboard into the three shapes shown below (parts A, B, and C), using the suggested measurements.