Sense of Depth

Computational tools afford us the opportunity to revisit historical collections, exploring and experimenting with sources in new ways. Stereoscopic images are ripe for this sort of engagement. Once popular pastimes that were viewed through binocular stereoscopes, they recorded scenes from two positions, to capture a scene as a pair of eyes would see it. The viewer was able to see the depth of the scene through the stereoscope, as each eye saw it’s own unique view of the scene.

The stereoscopic images that remain offer not only the visual record of those scenes, but retain that depth information captured by those two viewpoints. Although stereoscopes are less likely to be at hand today in order to view those images, we can still explore the depth they provide using image processing software to get a sense of the depth information recorded among them.

My research of magicians has often led me into the topic of mediums and seances, and in particular, I’ve found the Thomas Glendenning Hamilton collection at the University of Manitoba a rich and visually compelling archival source. Hamilton was a physician in Winnipeg in the early twentieth century. He recorded seances in a variety of formats, from taking notes to capturing images during seances with remotely controlled banks of cameras. In particular, stereoscopic cameras were included among the apparatus he used to record moments of those events.

I wondered how much more, if anything, I could see of those images — could I get a better sense of being in one of those seances? In what ways could the stereoscopic images be used without the original image at hand, and without a stereoscope?

A couple of stereoscopic images from the collection stood out to me for the action they portrayed. It looks like some seances were dangerous places to be in the 1920s.


Image courtesy of the University of Manitoba’s Hamilton Family Fonds


Telekinesis #26f – Levitating table

Image courtesy of the University of Manitoba’s Hamilton Family Fonds

Wobble images were my first attempt to view these. This process takes each stereoscopic image — the left and right views of the same scene — and uses them as frames of a very small movie. The images alternate, each viewable for just under a second. This flickering image, though, gives a sense of the depth in the scene as objects within it are situated in slightly different positions due to the two vantage points.



These two images should look like they’re wobbling or flickering. If not, open them in a new tab or window to see the full effect.

To make these, I used GIMP — a free image manipulation program. I imported the original stereoscopic image, and cut each image out of it. I saved each of these so I’d have a left and right image on its own. I then opened the left and right images as layers, and used the Animate filter in order to generate a animated GIF of the scene. When exporting the results as a GIF file, there’s an option to specify the duration of each frame. For these, I used 800 milliseconds. When viewed, an image is shown for just under a second, then it switches to the next image that is shown for 800 ms, and then back to the first. The cycle just loops continuously.

Viewing these, our brains create a sense of some of the depth in the images from the changes of position between the two scenes. In particular, we can sense the inside of the box, the flying table, and where people are situated. In the first image, I was drawn to the medium’s raised foot. Is she dodging the table, or could she have kicked the table? The expressions of the observers stand in contrast to the action of those within the seance circle.

In the second image, the observer’s facial expression is very puzzling, especially when combined with the position of his hands. Is he holding back the table, throwing it, or removing it from where it landed?

The flickering of the second image seems more harsh because the one image is brighter than the other. The jerky motion of this simple animation is also at odds with the original production of the stereoscope — a static photographic capture of the scene.

I still don’t have a stereoscope, but I do have red/blue 3D glasses from various sources. GIMP can also be used to create anaglyph renderings of the scenes. These can be viewed with any red/blue or red/cyan 3D glasses, and the depth effect is dramatic and much easier to explore than in the wobbling images above.



To make these, I imported each view into GIMP as a separate layer. Above each, I put a coloured layer transformed into a screen. Above the right view, I placed a red screen. I made a copy of the red screen and inverted the colour of this duplicate. This left a cyan layer that was transformed into a screen. The red screen was merged with the right view, and the cyan screen was merged with the left view. Those two resulting layers were then combined to produce the results above.

These translations of the digitized stereoscopic images make the views they offered via the original stereoscopes accessible through contemporary media, and allow us another opportunity to explore the depth information recorded nearly 100 years ago.