What is Stereoscopy?

What is Stereoscopy?

Well, it’d be a bit naughty to start a blog about stereoscopy and not say what it is!

In a nutshell: Stereoscopy uses the illusion of depth to create a single 3-D image from two flat images when viewed by each eye separately.


Stereoscopic pictures are a pair of images showing the same scene or object from two slightly different angles, corresponding to the angles of vision of the two eyes of a person looking at the object itself. Relying on binocular vision, the left image is presented to the left eye and the right image is presented to the right eye, the brain then interprets the two separate images, combining them in terms of depth… et voilà… you can see the image in its stereoscopic 3-D glory. Usually, when a person first sees a stereo-image in 3-D you know it’s worked when you hear the “WOW!”

There has been ongoing research and debates for years about how exactly the brain fuses two separate images into 3-D. If you’re interested in the science behind it, a good place to start is this summary of a 2017 paper from Ohio State University. They compared volunteers’ responses to viewing 2-D and 3-D images in an MRI machine to understand what cortical processes are happening in the brain, from the early to the late visual cortex. This is just the beginning of their research and the science nerd in me looks forward to their ongoing studies and findings.


An Example of a Victorian Stereoview



How each image is presented to each eye separately can vary. Some people can ‘free-view’ just by looking at a stereoview (of the correct size) and many say it works by looking through the images. Usually, this takes practice and experience and much boasting when successful. Some people switch the images around and go cross-eyed to cross-view, you look a little silly but you’ll be pleased to know that the wind can change and you don’t stay like it. A more in-depth (pun intended) post about this can be found here.


10-Owl VR Kit

A London Stereoscopic Company’s OWL VR Kit

An easy way for viewing stereoviews is by using a stereoscope, there are many options both new and old – a quick search on eBay, for example, will show there are lots. My personal favourite for using with standard-sized stereoview cards, my smartphone and many books is the London Stereoscopic Company’s Lite OWL but there are several other manufacturers. Just be cautious though that the viewer is the right size for the stereoview you want to look at, View-Master reels need a View-Master stereoscope, Lestrade cards need a Lestrade viewer, etc. You can also use the red and cyan glasses for red and cyan anaglyph images, polarising glasses for passive projecting and shutter glasses for active projecting. …OK I’m getting a bit too nerdy, but the idea is there are several ways to view stereoscopic 3-D.


07-Stereo Realist

A 1950s Stereo Realist Camera

Stereoscopic images can be made with binocular (twin-lens) cameras or single-lens cameras, with two separate images made for the left and right views. The Victorians began making stereo-daguerreotypes with single-lens cameras, but even before photography, they drew diagrams. They were amazingly inventive. The easiest way to make your own is with your smartphone and an app, which I’ve made a tutorial about here. Throughout this blog, you’ll find tutorials explaining how you can take your own stereoscopic photos using different equipment and methods.



Sir Charles Wheatstone – Inventor of Stereoscopy

History lesson time – I can’t mention what stereoscopy is without mentioning the inventor of the stereoscope and hero of stereoscopy, Sir Charles Wheatstone (1802-1875). He was born in England over two centuries ago and invented the stereoscope in the early 1830s, before presenting it to the world in 1838. 3-D was invented in the Victorian era even before photography, think about that next time you’re chewing popcorn at the cinema with a character popping out of the screen at you, incredible! If you’d like to learn more about the history of stereoscopy, written much more eloquently and in-depth than this potted ramble, please see the book ‘Stereoscopy: The Dawn of 3-D’.

Wheatstone stereoscope

Wheatstone’s Original 1838 Stereoscope, King’s College, London

Wheatstone’s original stereoscope used angled mirrors, one for each eye, and two separate images on either side, near your ears. This wasn’t the most convenient method and several years later, in 1849, the Scottish and grumpy Sir David Brewster (1781-1868) popularised a lenticular stereoscope that used lenses instead of mirrors, which meant stereoviews could be made much smaller as the two images were side-by-side for viewing.


A Brewster-Style Stereoscope

This eventually sparked the craze for stereoscopy and caused the mass production of stereoviews in the Victorian era, many of which you can still find today. If you read most books about stereoscopy, they incorrectly credit Brewster as the inventor of the stereoscope. Again, please refer to the London Stereoscopic Company book ‘Stereoscopy: The Dawn of 3-D’ for the thoroughly researched history.


Sir David Brewster – Angry Scot

There are tutorials throughout this blog to help you with all different kinds of methods of taking and viewing stereoviews. If you have any questions, please don’t hesitate to get in touch.

Thank you for reading,

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