Perhaps you have heard the story of the young man who stops his car along a small country road somewhere in New England to ask for directions from a crusty old farmer repairing his fence.  After a thoughtful pause, the farmer replies with a tone of finality, “Well son, you just can’t get there from here.”

In my opinion, there is something akin to this situation that is currently happening in the world of display technology.   Either that or perhaps I too have become like that crusty old New England farmer.   But before I get to what is bothering me, let’s first look at where we have come over the past 50 to 100 years with imaging technology – and for purposes of this discussion I will consider not only electronic displays but also photography and printing technology. 

More than a century ago, we started out with monochrome photographs and then fifty or so years later began to explore electronic displays.  Over time we were able to improve both imaging methods to exceed the resolution capabilities of the human eye.  Photography achieved this through the use of larger film formats and high quality printing papers.  By the middle of the last century is was possible to produce large hang-on-the-wall photographic prints that were as detailed as our eyes could perceive – at least at the anticipated viewing distances.  Electronic displays also were eventually able to achieve nearly the same resolution levels with monochrome CRTs for specialized applications such as medical imaging.  Once technology surpassed the resolution capabilities of the human eye, there was no compelling need to go further.  We had achieved all there was to achieve.

Next came color.  Color technology followed the same path of progress that had taken place with improvements in monochrome imaging.  In the early color photographs, the colors were not very good.  The same was also true for the first electronic images on the early color CRTs.  However, over time they got better and better.  Color prints and color photographs became more accurate and eventually could be used even for critical color matching applications.   Over time, color reproduction technologies have been able to get so close to what we see in nature that our eyes are not readily able to tell the difference. 

When we combine the capability of eye-limited resolution with accurate color reproduction, we begin to feel that the images have a “three-dimensional” quality.  In other words, our visual systems become convinced that what we are observing is an extremely accurate representation of reality. 

When we see movies made using such high-resolution techniques, we can easily become “immersed” in the experience.  The movement of the camera can provide us with a surprisingly compelling 3D effect.  When viewing scenes such as from a helicopter flying over the edge of a canyon, we get the realistically scary feeling of being thrust into open space with nothing below.  

Over the years, imaging technology has taken us to the limits of resolution and color reproduction capability – matching or exceeding the best that our eyes can appreciate.  Of course we don’t get this level of excellence in all images that we encounter.  Our flat-panel televisions don’t yet have the color capability that approaches printed material or photographic film.  Most movies are not made using the ultimate resolution that film, or electronic-imaging technology offers, but they are nevertheless adequate for the typical movie-going experience.

Having achieved such good results with still and moving images, isn’t the next logical step to add the third dimension and finally create something that is truly indistinguishable from the reality we see around us?  Isn’t 3D imaging the logical extension of all that we have already accomplished?   And even if it’s not quite perfect in the early stages, isn’t it going to get better and better until it’s just as perfect as our eyes can perceive?   We did it with resolution and color, so why not with 3D?  

Unfortunately, this is where we come face-to-face with the story about the farmer saying “Son, you can’t get there from here.”  Realistic 3D is more than just presenting two images to our eyes – no matter how well we do it on a movie screen or a flat-panel television, with or without glasses.  To do realistic 3D we will need to add depth-of-focus and also to compensate for head movement of each viewer.   And since these effects depend on where each viewer is looking and how they are moving their heads, there is no way to do this for a large audience – or even for two viewers at one time.   The technology may exist for one viewer (using eye-movement sensing and head-position tracking) but we have no currently known way to do it for an audience of two or more using only two stereo images.  

The best that we can end up with is a three-dimensional effect that conveys a feeling of depth that is interesting and entertaining but will always be perceived as “not quite right.”  This should not be a problem for gaming applications, for animated or computer generated movies, or for fantasy movies such as science fiction.   But for general viewing that is supposed to represent real-world scenes, our brains will simply not accept these images as accurate depictions of reality.  Stereo images that don’t present the right depth-of-focus and that don’t respond correctly to our head movements will cause our visual systems to struggle with these subtle conflicts and will result in eye/brain fatigue and an eventual loss of interest in using this technology. 

Photography has struggled with 3D images for many years.   Adequate resolution and accurate color reproduction have not been the limitation.  In the mid-50s, stereo Viewmaster slides were quite popular as vacation souvenirs.  But even with good quality 3D projectors, there wasn’t sufficient additional value to create a sustainable market for these products.  Here is what the Editors of Popular Photography Magazine had to say about 3D photography in the August 2009 issue in reviewing technologies that “bombed.”   “Seemingly every year since the invention of photography, we’ve had stereoscopes, lenticulars, anaglyphic glasses, polarizing glasses, wiggle stereo, digital 3D mode, the Stereo Realist, the Nimslo, the Loreo…”  Their conclusion is that 3D is “Photography’s version of The Undead.”  

Perhaps the end result for 3D movies, television, and digital images will not be so grim.  The acceptance may be sufficiently high for computer-generated images to create an ongoing market.  But if any of you have the expectation that 3D images will soon become so realistic that our visual systems will accept them as an accurate reproduction of real scenes, then perhaps you will need to listen carefully to the advice from that crusty old New England farmer – “Well son, you just can’t there from here.”

The presentation of two stereo images, no matter how accurately and precisely done, is not sufficient to give us “reality” – and never can be.