Stereoscopy — An Actual 3D Sense of Depth and Perception

Intro­duc­tion

Those of us in the field of 3D often use the term “3D” very loosely — when artists often refer to the term, we typ­i­cally mean to dis­cuss a 2D image that has a more real­is­tic per­spec­tive (light­ing, shad­ows, and angles) that would be rep­re­sen­ta­tive of a stan­dard pho­to­graph. Just like our stan­dard “3D art­work”, a pho­to­graph has no actual depth of per­cep­tion and in real­ity isn’t tech­ni­cally “3D.” Truth­fully, I do not know what to call this mis-labeling or mis­nomer — it’s a term which has been mis­used by the “3D” com­mu­nity for sev­eral decades now and I have even come into the habit of fre­quently using this because it is some­thing most peo­ple have come to relate-to. Per­haps a term such as “CG Per­spec­tivism” would be more accu­rate and appro­pri­ate for these works.

A “tra­di­tional” 3D ren­der­ing by myself. Although this resem­bles an actual pho­to­graph, it does not con­vey an actual sense of depth perception.

In regards to 3D as in the true term of “a sense of depth”, there is a bit more to the tech­nol­ogy than meets the prover­bial eye. It involves a cer­tain level of under­stand­ing our own human phys­i­ol­ogy as well as devel­op­ments in 3D technology.

The First Descrip­tion of Stereoscopy

In order to lend an image an actual sense of depth, it requires that we have stereo­scopic vision — a left and a right eye. Sir Charles Wheat­stone was the first per­son to describe this phys­i­o­log­i­cal effect called stere­op­sis. His term dates back to 1838. Text from his orig­i­nal research paper can be read here:

http://www.stereoscopy.com/library/wheatstone-paper1838.html

Sir Charles Wheat­stone, 1868

Sir Charles Wheat­stone also went on to invent the Pseu­do­scope in 1852 which even­tu­ally became the fore­run­ner into mod­ern stereo­scopic imag­ing technologies.

3D View­ing Technologies

There are sev­eral dif­fer­ent “mod­ern” meth­ods and tech­nolo­gies which can trick our vision into believ­ing that a pho­to­graph, movie, or “3d” scene really has a sense of depth. All of this still has it’s basis in the pio­neer­ing research of Sir Charles Wheat­stone. These meth­ods often involve sep­a­rat­ing an image apart into two dif­fer­ent com­po­nents, a “left” and “right” image of the same object or scene. An opti­mal for­mula for deter­min­ing and cal­i­brat­ing depth per­cep­tion involves mea­sur­ing the dis­tance between the left and right eyes in rela­tions to the focus or dis­tance of an object and apply­ing it to an image that we are viewing.

Here are a few side-by-side meth­ods for view­ing an image in 3D:

1. Stere­o­graphic Cards and Pic­tures. These are two images side-by-side taken or pho­tographed from slightly dif­fer­ent angles. These cards often involve forc­ing one’s eyes to cross in order achieve this sense of depth.
   

   A Stereo­scopic Image of Baker’s River, Rum­ney, New Hamp­shire 1889

2. Trans­parency View­ers. These are devices such as the View-Master that you hold up to your eyes and view stere­o­graphic slides.
   

   1962 View-Master cour­tesy of Wiki­me­dia, IllPassaggero

3. Head Mounted Dis­plays. These involve hel­mets or glasses with LCD or OLED dis­plays. This may involve pho­tographs or Vir­tual Real­ity scenes. This is per­haps the most recent tech­nol­ogy at the time of this writ­ing. It can pro­vide a wide-range of depth and motion.
   

   Ema­gin Z800 Head Mounted Display

Here are sev­eral main meth­ods of 3D viewers:

1. Liq­uid Crys­tal Shut­ter Glasses. This active method involves wear­ing glasses that can alter­nate and sync shut­ting on and off the left and right sides of these glasses in syn­chro­niza­tion with the refresh rate of your mon­i­tor or TV. As of 2010, the major­ity of “3D tele­vi­sions” on the mar­ket fall into this cat­e­gory. Most stan­dard com­puter mon­i­tors and flat-panels only have a refresh rate of 60 Hz, whereas a “3D tele­vi­sion” or “3D mon­i­tor” has dou­ble (120 Hz) sig­nal. Costs asso­ci­ated are typ­i­cally high, and hence movie the­aters do not employ this technology.
   

   Liq­uid Crys­tal Shut­ter Glasses

   Polar­ized Glasses. Images are super­im­posed on to the screen through orthog­o­nal polar­iz­ing fil­ters. In turn, the viewer wears glasses with orthog­o­nal lenses. These lenses are gen­er­ally clear, but darker in color and result in some loss in bright­ness. This method is com­monly used in movie the­aters as of the time of this writing.

   

   Polar­ized 3D Glasses

Anaglyph Glasses. There are sev­eral sub-types of this 3D Viewer cat­e­gory, but for the sake of this arti­cle I will keep it brief. If you would like to read more on the topic, I would rec­om­mend vis­it­ing the Wikipedia arti­cle here. Anaglyph glasses are the more tra­di­tional method of view­ing 3D images, often with the sep­a­rate red and cyan lenses. As of more recent tech­no­log­i­cal devel­op­ments involv­ing higher res­o­lu­tion film­ing and dis­plays as well as bet­ter method­ol­ogy, dif­fer­ent lens col­ors are being used to help add nat­ural color back into these images and also to bet­ter align left-right images more accu­rately. Fur­ther refine­ments has helped reduced the appar­ent color tint in some of these lenses. Some of the newer meth­ods even help make an image appear nor­mal with­out the use of glasses. Some 3D artists includ­ing my work and com­pany, LunarStu­dio can pro­duce cost-effective anaglyph images which are view­able with glasses.

Tra­di­tional Anaglyph Glasses

Other com­mon 3D dis­play methods:

1. Lentic­u­lar Prints. This con­sists of a plas­tic laminate/substrate made of fine, vertically-running prisms lay­ered on top. Under­neath this layer is a left/right series of alter­nat­ing images. By mov­ing your head or tilt­ing the image, you can con­vey the sense of depth and even motion. These are often seen in 3D post­cards. With the advent of bet­ter tech­nol­ogy con­cern­ing print­ing res­o­lu­tion, the prisms and shift between left/right images has become smaller. Depend­ing on the prism struc­ture and the amount of images you super­im­pose, this could pro­vide a much wider range of angle depth than typ­i­cal 3D view­ing meth­ods. You can even find kits and soft­ware online to pro­duce these on your home print­ers. Here is a video of the lentic­u­lar process cour­tesy of Photro­gram:
   
2. Dis­play with fil­ter arrays. This is a sim­i­lar con­cept to lentic­u­lar prints, but involves two LCDs on top of one another and shifted slightly. This doesn’t require glasses but may limit the sense of depth at spe­cific view­ing angles.
   
3. Holo­graphic Prints. Holo­graphs could be almost thought of as a very fine pris­matic lentic­u­lar print, but instead of being only view­able on a hor­i­zon­tal plane, it can be turned in many dif­fer­ent planes of direc­tion and still be view­able. It relies on emboss­ing a medium on very fine, micro­scopic level. This emboss­ing in turn dif­fracts the wave­length of light which appears to change depend­ing on how we turn the medium. Recent advances in holo­graph and com­puter tech­nol­ogy have improved image and color qual­ity sub­stan­tially. One com­pany that is pio­neer­ing holo­graphic tech­nol­ogy for print is Zebra imag­ing. My com­pany, LunarStu­dio is able to make 3D illus­tra­tions and mod­els which can be printed by their ser­vices. I’ve posted an exam­ple of their lat­est work below.
   

A Pro­posed 3D Technology

One of my thoughts on 3D tech­nol­ogy is that what lends peo­ple the sense of depth isn’t really color, but rather a lack of light hit­ting cer­tain angles. We can all agree that the com­po­nents of the vis­i­ble light spec­trum can be dupli­cated using the col­ors of red, green, and blue — or the RGB addi­tive model (addi­tive in the sense that if you add RGB together, it should form a pure white.)

For exam­ple, if I held a red sheet in front of a viewer in flat/neutral light­ing con­di­tions per­fectly per­pen­dic­u­lar to the sheet, no mat­ter how I turned it — the red will appear red. How­ever, if I altered the light source to remain fixed, the red sheet will start to dis­play gra­da­tions of black and grey — or shad­ing and shad­ows. It is the black and grey (or absence of color) that lends an object the sense of depth aside from our sep­a­ra­tion of back­ground noise and blur.

Instead of shift­ing pri­mary col­ors in a tra­di­tional anaglyph sense, I believe you could prob­a­bly shift the black/grey (or K) val­ues slightly to achieve a sim­i­lar 3D stereo­scopic effect. This may result in some­thing sim­i­lar to cam­era Depth of Field/blur which is a often an exag­ger­ated form of depth per­cep­tion. Com­bine this grayscale sep­a­ra­tion tech­nique with a fine lentic­u­lar type of lens that alter­nates between gra­dated shades of black/grey instead of pri­mar­ily rely­ing on the RGB color com­po­nents, I believe you could poten­tially achieve a much bet­ter stereo­scopic effect. In the­ory, I sup­pose my idea is some­what sim­i­lar to polar­iz­ing tech­niques, but retains much of the orig­i­nal color fidelity while per­haps los­ing out on some edge sharp­ness. How­ever, at fine res­o­lu­tions, the effect may not be as noticeable.

In my mind, it’s an inter­est­ing con­cept. I do not have the time, money, or energy to invest myself in exper­i­ment­ing with the poten­tial here. I would be hon­ored if some­one was able to take my idea and turn it into a work­ing pro­to­type. Also, per­haps some­one has already exper­i­mented with a con­ver­gent idea and that I’m not aware of its prior existence.

Con­clu­sion

There are many dif­fer­ent meth­ods for us to per­ceive a sense of depth within an image, or “true 3D” as I’d like to call this. The field is con­stantly evolv­ing, improv­ing, and there are no short­ages of ideas to be explored. Most of our lim­i­ta­tions revolve around under­stand­ing and tech­niques com­pounded with pro­duc­tion costs. Obvi­ously, a sim­ple red/blue anaglyph pair of lenses is much more cost-effective to pro­duce and sim­pler to deploy to a large audi­ence than a fully immer­sive Head Mounted Dis­play. Due to these costs, most of us have been unable to expe­ri­ence some of these more recent tech­no­log­i­cal devel­op­ments first-hand. On the other hand, higher costs for the most ground-breaking tech­nolo­gies are also push­ing increas­ingly bet­ter and less expen­sive tech­nol­ogy to a more recep­tive, consumer-friendly audi­ence. Our desire for this for­mat as a soci­ety is grow­ing insa­tiably. Some how­ever remain “uncon­vinced” — they insist on refer­ring to this pro­gres­sive 3D trend as a gimmick.

There will come a day when 3D stereo­scopic cam­eras become com­mon­place and our view­ing tech­nolo­gies improve to the point where we don’t have to rely on other devices such as glasses. These movies will look com­pletely nat­ural, and a reverse social psy­cho­log­i­cal effect will occur — when view­ers look back at our old method of cin­ema, games, and pho­tog­ra­phy — they will con­sider any­one pro­duc­ing work with these tech­niques using the tra­di­tional 2D flat-style as the ones pulling a styl­is­tic gimmick.