Stereoscopy

All of you encounter the con­di­tions of stere­oscopy reg­u­lar­ly when you are in a vehi­cle and look side­ways at the pass­ing land­scape. Do you recall that the far away moun­tains seem to stand still and trees and hous­es in front of them move slow­ly while the road signs rush past? We can eas­i­ly con­clude that the dis­tance of an object is respon­si­ble how fast it moves through our field of view while we move past it.

Because we have two eyes our binoc­u­lar vision always con­sists of two points of view — slight­ly off­set. You can also see objects “mov­ing” if you look at first with the left and then with the right eye while you close the oth­er, but you might hard­ly notice.

Our brain always com­bines our binoc­u­lar vision into one three-dimen­sion­al, stereo­scop­ic image — with an inner sense of depth called stere­op­sis. It is impos­si­ble to lit­er­al­ly show this with a three dimen­sion­al image on here, because a screen can be noth­ing but flat. All hap­pens inside your head at the neur­al lev­el and your brain absolute­ly needs two indi­vid­ual images. But the process of stere­op­sis can be enhanced by stere­oscopy.

Stere­oscopy means the tech­nique to cause stere­op­sis using two flat images.


Near Frank­furt cen­tral sta­tion, Ger­many 2019.
Look at the dif­fer­ent posi­tion of the build­ings and the cate­nary masts in each pho­to.

Richard stere­o­scope, France c. 1910.
Stereo view­ers can be help­ful for a prop­er per­cep­tion of the two images to ensure stere­op­sis. Author’s col­lec­tion.


If you want to know how you can view stereo­scop­ic images with­out a view­er or what kind of view­er is best for you and where to find it, have a look at this tuto­r­i­al on Rebecca’s stere­oscopy blog.

As illus­trat­ed in the train image above, stere­oscopy starts with two suit­able images. Every­one who wants to take his own stereo pho­tographs, must pay atten­tion to a num­ber of require­ments that depend not only on the cap­tured scenery but also on the pur­pose. This means that a stereopho­to from Insta­gram may look amaz­ing on your smart­phone, but will over­tax your eyes if pro­ject­ed on a cin­e­ma screen. On the oth­er hand there are also quite a lot pos­si­bil­i­ties for trans­form­ing the rules to cre­ate artis­tic effects with depth. Read more about that in the sec­tion Stereo pho­tog­ra­phy.

Final­ly, might want to spend a lit­tle time read­ing the brief his­to­ry of stere­oscopy on the 3D Alps web­site to learn more about the devel­op­ment and dif­fer­ent appli­ca­tions of stere­oscopy and it’s impact through all ages.

Chil­dren por­trayed with a Brew­ster type stere­o­scope — sure­ly their most favorite gad­get, Eng­land and France c. 1890. Author’s col­lec­tion.