From afar a coastline might look as though it is smooth and inviting, whereas a closer-up, higher resolution view might reveal a rocky, forbidding shore. Similarly, standing directly beside a large circle painted on the asphalt might make it appear elliptical or oblong-shaped, as compared to looking at it from directly overhead. Even with adequate context, appearances can still sometimes be misleading. What we perceive as the truth is often just an emergent phenomenon and perhaps only a partial picture of the whole. Notions of scale, context, as well as the abilities and limits of our own perceptual systems, all play a role in interpreting how things look, sound, smell, and feel.

In stereophotogrammetry, photographs of a particular region, purposefully taken seconds apart from an aircraft flying high above, might initially appear identical. A closer look reveals minute changes, such as shadows shifted due to the slight difference in perspective. Nowadays this type of imaging data can be fed into complex algorithms, and in some instances combined with range-finding laser data (LiDAR) to generate accurate three-dimensional views of the landscape.

In days gone by, viewing such a stereoscopic pair of photographs, or stereogram, required a contraption called a stereoscope. You may recall the more recent plastic View-Master with its shutter-like lever that came with round disks of tiny, paired images, 3D glasses, or Virtual Reality (VR) systems based on the same principle, that are in common use today. These technologies present just the left perspective image to the left eye, and the right perspective image to the right eye, from a set distance. When the nearly twin images are viewed in this manner, the resulting three dimensional illusion does not appear on the glass of the device, or as on the page or screen of an artist’s drawn visual perspective, but rather materializes with realistic clarity directly in the viewer’s mind. Viewing an air-photo stereo pair would have hills and mountains rise up from the erstwhile flat land, while the valleys and lowlands receded. A rich gestalt sense of an area could be derived from such a  three-dimensional portrayal, not otherwise apprehensible from an individual air or satellite photo. Convincing appearances thus need not necessarily exist in just the physical world, and are sometimes purely figments of the perceptual system, or even of the imagination.

More broadly, beyond our hacking of binocular vision, nature has conferred on us the intrinsic ability to illude; to imagine what is and isn’t there. The world around us is perpetually being crafted as we perceive, as though we’re each an artist interacting with it, conjuring illusions and interpretations of what’s in front of us, and what lies beyond the range of our perceptions. Neurologist and author Oliver Sacks remarked that, “each act of perception is to some degree an act of creation, and every act of memory is to some degree an act of imagination”.

Sacks, O. (2007) Musicophilia. Toronto, Canada: Knopf