Why Can’t A Regular Photograph Be Converted To 3D?

While a Google search will certainly yield many hits for “2D to 3D conversion” this is terribly misleading. You can create 3D “things” out of a 2D photograph but you can’t convert a 2D into a real 3D photograph in a real sense because the content to do that isn’t present within a single perspective photograph.  There will be missing obstructed imagery that can only be interpreted. But even more worrisome than obscured objects within the photo is that binocular rivalry will be totally inaccurate as it isn’t possible to interpret this phenomena from a single photograph.

What is binocular rivalry?

It is unique to two-perspective fused vision. It isn’t perception of depth, but what it adds is a richness that is what stereopsis vision achieves when we look at the real world. Binocular rivalry exists as an optical comparator of similar things within a multi-perspective photograph or even a two perspective stereocard. Any differences are perceived with an oscillating relief or flicker when there is great disparity. Where differences are more subtle, as with the qualities of texture and surface, such as the appearance of metallic objects or gemstones, we sense the attribute of rivalry in a way that greatly lessens ambiguity. We can more accurately identify metal material than even the most precise camera imaging analysis equipment. Stereo vision provides a binocular comparison of a surface and our brain separates its true appearance from the interference of reflected light. We both ignore the noise of the subject’s illumination and perceive it with the ability to lessen its ambiguity. This can be easily demonstrated when looking at metallic pigments or fabric impregnated with metallic substances.

Just as when color is reduced or eliminated we can still see. Certainly black and white television was very popular at one time. But just as color was missing and appreciated when it became available, the same is true for the accurate representation of binocular rivalry. 2D to 3D conversions can’t do this accurately. You might enjoy looking at the result just as people enjoyed looking at black and white TV. But these conversions are missing fundamental information that is substituted with false imagery.

If you want accurate 3D you must have more than one perspective to work with.  You have two eyes and a brain to process all of the information from two perspectives into a single fused image with depth. Binocular rivalry, convergence and disparity are all essential and require more than one perspective to be accurate in the same sense that what we see in the world is accurate.

So, the real title of this blog entry should be “A Regular Photograph Can Only Be Converted To A Fake 3D Image – It Can’t Match A Two Perspective Image”.



Filed under 3D Photography, S3D, stereopsis

6 responses to “Why Can’t A Regular Photograph Be Converted To 3D?

  1. Almont, you have put it correctly in a very concise and well structured article. well done.

    While many argue that even CGI stereoscopic 3D films are not real as it’s a “rendered” world, what they forget to think of is that these “renders” are actually following a ray of light (raytracing) obeying real-world rules of refractive / reflective indexes of materials, and not just mapping a 2D video texture on primitives.. yes blocky primitives! and being hand filled by a person where gaping holes exist. This is just so wrong.

    however, that’s the way it will be, and no sense arguing it, so the best we can do is try and encourage to shoot / create true stereoscopic images… but otherwise just give in (much like 128kpbs mp3 v/s vinyl or CD debate)

    What will be fun in the coming year will be the neat game you can play in Cinemas if your bored – called Guess the “fake bits” 🙂

    see these two movies I had reviewed:

    • Actually, I believe it is very important to argue because evidence from neuroscientists indicate that viewing false 3D does not induce a positive experience and that the negative impression can be strong, even creating a bias against the technology. Note that many critics complain that “3D gives me a headache”. This can be characterized as shooting ourselves in the foot. If you say a food tastes really good and then people eat it and it tastes bad then you have lost credibility and are doing things that will ultimately put you out of business. This is extremely bad for the industry and if we don’t collectively start shouting that the emperor has no clothes, pretty soon it is going to be our undoing. We need better movies to succeed Avatar for 3D to succeed, otherwise this will just be another blip in the history of 3D.

  2. Daniele

    This is the first time, I red that binocular rivalry is desired.
    Neuroscientist write about binocular rivalry as a phenomena of a »one eye suppression«, especially in latent stereopsis (forcing you to close one eye to achieve better viewing results). There are many forms of binocular rivalries and the most I had experienced cause headache.
    I have seen a lot of stereo conversion testings these days, and some do not work, because they have binocular rivalry, like depth cue rivalries or so.
    Binocular rivalries caused from too much disparity will elicit eyestrain – in my eyes.

    But I like the idea of rivalry as a proof of the real and imperfect world we life in. It does not fit to the cyclopean depth perception model in the first place, but I give it a chance.
    And Yes something is missing in stereo conversions.

    • I am only talking about accurate binocular rivalry as experienced in real life being the standard. Not artificial binocular rivalry which I believe is not a good thing. Since each eye sees a different perspective with photons hitting disparate rods and cones in each eye – that is total defacto binocular rivalry. No part of the image on each retina matches exactly. So at the photon level there is disparity – on up to huge levels by comparison. The brain processes this, interprets it and presents a single image with depth and interpretive information based upon the differences which relate to materials properties — and other things that go way beyond my level of understanding.

      It is these subtleties that reveal “realness” as interpreted by the brain. I believe that is important and I question the motives of those that dismiss it so readily as not important. 3D is much more than simply providing perspective information through offsetting objects in relation to one another.

      • Daniele

        I completely agree with binocular disparity. Compare Julez »Spring-loaded dipole model«.

        But you may mix up the terms binocular rivalry:
        Here two citations:

        »If the images on the retinae are not similar or if the disparity increases above the limit of patent stereopsis, binocular rivalry is experienced. Under this condition parts of one image dominate parts of the other image, and they alternate dominance in time«

        Jules, Bela: Foundation of Cyclopean Perception. MIT Press. London 2006. P 23

        »Stimulation of corresponding proximal regions of the two eyes by very different high-contrast images results in binocular rivalry. Rivalry is the antithesis of fusion. Instead of fusion, the two monocular images may alternate repetitively, in whole or in part, with the unseen portion somehow suppressed (Levelt,1968). The alternation my continue as long as the stimuli are presented and the temporal sequence may be irregular«

        Hershenson, Maurice: Visual Space perception, A Primer. MIT Press. Cambridge 2000. P 57/58

        That is what I red about binocular rivalry. Maybe I got something wrong?

        But anyway… the terms might not be important.

        Your final conclusion is, that stereoscopy is more than horizontal shifted cardboards – I agree.

        best regards


  3. Sort of… My real life experience is that fusion isn’t defined with precision. What does: “increases above the limit of patient stereopsis” mean exactly? I don’t think there is a definite definable limit or transition point. I see it as a moving target based upon a wide range of fusion possibilities. I think fusion and rivalry coexist at this transition point(s) and the disparities are interpreted in the brain in amazing ways that are not understood. I think only in the extreme are they separate –perhaps I should interpret that as the true meaning of binocular rivalry – where fusion isn’t possible at any level. But do we experience that in real life as part of normal “seeing”. Dr. Barry talked a great deal about her varying “levels of seeing in 3D”. I think she might be referring to levels of fusion and the brain’s processing and interpretation of how to fuse.

    For purposes of precise clarity, perhaps the term binocular rivalry wasn’t the best choice – but I like to use it because I want to point out that there is more to stereo vision than position shift of objects as they receed into the distance and that we see different things in each eye. Oftentimes we see parts of things present in one eye that aren’t present in the other eye (as in the case of metallic reflections). In this example, the area of reflection imaged on each retina is completely unique and can’t be fused but the rest of the image is fused. The brain interprets the non-fused part of the image in a way that tells us something unique about what we are looking at. I have read articles where that is called binocular rivalry so perhaps the term is ill-defined?

    Thank you very much for your comments! I hope that this blog, if it does anything, will serve to point out that seeing 3D is not just a button you click on your computer. It is a miracle we experience everyday that we take for granted and little appreciate. This arrogance has lead to years of missteps in the development of 3D movies and photographs.

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