Stereoscopy: the birth of 3D technology

In his paper published in the Philosophical Transactions of the Royal Society, Wheatstone outlined experiments to force each eye to look at separate objects or images and describes the resulting effects, to prove depth perception is a phenomenon of binocular vision. Leonardo Da Vinci had previously explored this, but not realised the scope of its applications.

Wheatstone had trained his eyes to see properly prepared pairs of images or stereograms in three-dimensions without a viewing aid. He designed the reflecting stereoscope to help those with less practiced eyes experience flat images in relief - an entirely new optical experience.

In 1849, David Brewster FRS improved and popularised a portable 3-D viewing device, the lenticular stereoscope. Using lenses and prisms instead of mirrors it was more compact than Wheatstone’s reflecting stereoscope and easier to use. It became the first commercial stereoscope and gained mass popularity after display at the Great Exhibition of 1851 and Queen Victoria's purchase of a lenticular viewer from Jean Antoine Claudet FRS in 1852. Claudet and Brewster went on to clash over further developments in stereoscopic technology

Brewster also sparked controversy by claiming Wheatstone had not invented the stereoscope or thought to use it with photos. In response Wheatstone published a second paper in 1851, defending the originality of his idea and claiming that he had commissioned photographs as soon as Henry Fox-Talbot FRS had revealed his photographic process to the Royal Society in 1839.

Brewster's wider work on optics, included defining the laws of polarisation. Understanding polarisation would be pivotal to the technology behind creating 3-D movies. The first practical 3-D filming and viewing system was developed by Edwin Land FRS nearly a century after stereo photography. Polarised light-filtering glasses were worn by the audience to force the binocular effect.

Photography vastly expanded the scope of subject material for stereoscopy. Landscape and city scenes were popular as they could create an immersive effect, transporting the viewer from their parlour. Many different stereoscopic viewers went on to be patented, taking advantage of the technology's popularity. Stereo photographs or stereographs were also widely used for scientific purposes.

Charles Piazzi-Smyth FRS (1819-1900), a pioneer in astronomy and photographic publishing led an expedition to the mountains of Tenerife in 1856 to test making astronomical observations at altitude. His popular account was the first book illustrated with stereoscopic photographs.

Along with his wife Jessica Duncan Piazzi Smyth (1812-1896), a geologist, they documented their experiments and equipment in the field, the geological formations in the volcanic mountains, and Tenerife flora and landmarks.

In the preface of his book, Piazzi Smyth explains his choice to publish stereographs. In addition to the three-dimensional effect, he saw it as an advantage to show two images to verify accuracy. For "correctness" a photo is better than a drawing - but two photos are better than one! This is also true when trying to capture a bullet in motion.

The motivation for this experiment is unclear, though a projectile makes for a dramatic stereoscopic subject. It may have been conceived to help with Sargeant McKinlay's duties as a Proofmaster. His role was to test the safety of gun barrels by using an over-pressure charge of powder to strain the barrel's resilience. In artillery proving is the only use for galvanic tubes, which may have given him the idea for the ingenious trigger system in his experimental photography.