3D - why is it ultimately unconvincing?

Whenever I see 3D, be it TV, at a cinema or a stereoscopic ViewMaster, it always fails to appear naturalistic. Sure there is often a great sense of depth to the scene as a whole but the individual elements of that scene always look flat. I am reminded of the old victorian cut-out theatres. Why should this be so? The cameras used to capture 3D mimic the stereoscopic mechanism of the human visual system so I would naivly assume the result should appear true-to-life, but is doesn’t.

It is? :dubious:

One aspect is the focal plane*, Normally you focus on a object based on distance, in 3D the distance is constant and the camera ‘decided’ what is the focal plane.

  • By focal plane I’m referring to the adjustment to the lens in the eye, which has nothing to do with using 2 eyes.

In addition to the focal plane issue mentioned by kanicbird (i.e., you are always focusing on the screen, which is where all the images actually are, rather than at the further or nearer distances where the images seem to be according to the 3D effect), there is the issue of motion parallax. In normal seeing, slight movements of the head cause parallax motion of near objects relative to far objects. In fact, in real life our sense of the third dimension probably depends as much or more on this than it does on the separation between our two eyes. In most circumstances, one eyed people are not much impaired in seeing the third dimension, because they get enough information about relative distances from this head-motion-parallax effect. Cinema (and other) 3D systems rely entirely on “fooling” that aspect of your sense of the third dimension that results from binocular disparity, and cannot handle head motion at all. Thus, in the cinema, every time you move your head a bit (it only has to be a tiny bit, the sort of motion we make all the time) your brain is getting conflicting information from the binocular disparity system (which is telling it some things in the movie are nearer than others) and the head motion parallax system (which is telling it that they must all be at the same distance).

I am not entirely sure, but I think the sort of “cardboard cutout” effect that one sees with a Viewmaster (where head motion is not an issue, because your head is kept still relative to the images) occurs because Viewmaster actually tries to exaggerate the 3D effect by placing the cameras that take the two pictures further apart than people’s eyes actually are. This makes the 3D effect more striking, in that near objects look even more strongly separated from the background than they would in reality, but also makes it look unnatural. I am not quite sure why this should make the objects themselves look flat, but I certainly know what you mean. I had a Viewmaster years ago, and I can remember thinking back then how everything looked like a cardboard cutout.

Another minor factor that might be throwing off you realism meter is the lighting.

Movies are often made with lighting that is designed for dramatic effect.Lighting that does NOT generally occur in the real world. And also to work around the limitations of what the camera can record and the display system can project.

Now, obviously, this problem is not limited to 3D recordings. But even if all the “problems” with 3D recording were eliminated, if the lighting wasnt real world realistic, it would still probably set off your “it aint quite right” meter.

Which reminds me, I need to go see that new 3D cave movie. Thats probably the perfect environment for showing off 3D.

A friend has the newest Sony 55 inch 3D TV. I was able to watch a bit of Alice in Wonderland. I was surprised to note I had to hold my head level at all times or there was a color shift in the image. I found this pretty annoying.

I don’t think there was much in the way of ‘ghosting’ in the image, but I would like to see a TV that is ‘bad’ in that regard to make sure I am looking for the right effect or nuance in the image.

I suppose this is not entirely on topic, but part of the reason I’m unconvinced by 3-D is that there is so much information in a 2-D image already to give an idea to your mind what the 3-D environment is like. For instance, by artificially changing how things are in focus, you can give the impression that a picture taken from full-size objects was created by miniatures (there was a thread on this topic recently). Thus, the relative focus of things gives your brain an idea of how things are spaced. Additionally, your brain takes into account the shading profile of objects, and can be fooled by using a non-uniform light source or a material that changes its actual shade. Neither of these require parallax/stereoscopic vision.

Thus when you add parallax to a flat image, you really don’t contribute that much more to a sensation of where objects are in relation to each other, and as mentioned above there is still an important aspect of 3-D recognition that’s missed - something that will be effectively impossible to replicate on a flat surface without providing each person his own image and keeping track of the minuscule head and eye movements that create the effect.

Roger Ebert just received a letter from Walter Murch, a well known editor and sound designer. He wrote an entire article on why 3D doesn’t work and will fail.

It’s worth reading, which you can here:

Why 3D doesn’t work and never will. Case closed.

Scroll down a bit and read his letter. It’s quite good.

Eh, I respect both Ebert and Murch, but I don’t think that article totally demolishes the argument for 3D effects. Some people have trouble adjusting to the image (which is why movies should be available in 2D) but for the few 3D movies I’ve seen my brain didn’t really have any trouble accepting the illusion. You can’t say it “doesn’t work” - you can only say it doesn’t work for some people.

I think this is a huge factor. Note the work of Johnny Chung Lee, see at this page


Scroll down to “Head Tracking for Desktop VR Displays using the Wii Remote .” This device uses a computer to show motion parallax on a screen, which gives a much greater sense of being in a 3D world. This is, of course, only good for one user at a time.

Oftentimes, the individual elements look like flat cutouts because they are flat cutouts. With the old Viewmaster-type stereograms, it was cheaper to construct the scene to be photographed out of cutouts than using actual 3D models, and many 3D movies use an equivalent technique to turn a 2D filmed scene into “3D”. But in both cases, it is possible to do it right.

If you could make the screen a giant hologram. If you could do it in multiple colors. If you could do the holgraphic recording in multiple colors. If you could get rid of “speckle”. And probably a few other if’s that I am forgetting at the moment.

If you could do all of those things, you could have the perfect 3D movie effect.

But thats a lot of ifs. Like flying cars, I don’t expect them anytime soon.

Murch’s argument isn’t that it “doesn’t work”, it’s that it “doesn’t work well, and can probably never be perfected, because of the inherent flaw in the way 3-D images are projected vs how a real 3-D object is perceived by the human visual system”

Could it also be an indivdual thing? I have never seen any kind of 3D that really works for me, for lack of a better phrase. Maybe it works for some people better than others

IMO I think that certainly can be the case.

It might also be that you’ve become so used to 2D movies that 3D doesnt seem right/do anything for you. Or, in other words, in some alternate you in an alternate universe where alternate 3D you grew up from day one viewing 3D movies “gets it and likes it” while poor old 2D you doesnt.

I suspect this has happened to some folks that went from silent movies to talkies, from black and white to color movies, and music from staticy radios/records to high def/low noise/good digital recordings.

Like me and real books vs the internet/some kinda kindle thingy. They just are not the same for lurnin or enjoying the readin even though the later are probably in all real measures better.

Maybe this is true of some of the sets used in the old 3D movies, but why on Earth would you need to construct any sort of “model” for a Viewmaster? All you need to do is photograph a real scene (which already come in 3D) from two positions a couple of inches apart. I am fairly sure this is now Viewmaster slides were made, perhaps with a special "double camera, or possibly just by moving the camera a few inches over and taking the shot again.

Indeed, and furthermore Murch only considers the issue of the focal plane, and ignores the further issue of motion parallax. Although it is the focal plane issue that tends to cause people to get headaches from 3D, my guess is that the motion parallax problem probably contributes more to the sense of “wrongness” one gets. (Although I do not think it can be the source of the “cardboard cutout” feeling, as such, since this occurs in Viewmasters, where head motion is not an issue. I have not really noticed the “cardboard cutout” effect as such in 3D movies, but that may just be because I have not seen enough of them.)

I’m convinced this could be used as an advantage* in an animated fantasy. Creatively using cutouts to build a story world like the ancient Greek mechanical play boxes would look fabulous. A short section of the otherwise-dreadful Tale of Despareaux used this kind of effect, albeit without 3D.

Rules of cinematography and editing for 2D don’t work the same in 3D. Longer shots work better, and parallax needs to be purposefully shown. A good tracking shot is a better 3D effect than an object thrown at the camera.

*: a drawback turned into an advantage is a reverse salient; electric guitar feedback is an example: first avoided, then manipulated purposefully.

Coraline 3-D used this to an advantage in one scene, to impress upon the viewer the flatness and artificiality (and, IMO, lack of time devoted to creativity that a character in the movie put into the creation of) of a certain place. Or maybe it was just weird for weirdness sake but it worked :slight_smile:

It hurts our suspension of disbelief because you’re trying to watch a movie and all this stuff is coming out of the screen. Oh yes, it’s coming right for us, watch out! It’s just gimmicky. Kinda like watching movies with really bad CGI. It’s just glaring.

Nothing that he wrote is wrong exactly, but I could write an equally devastating article on the flaws in 2D projection systems.

All technologies are flawed. The only question is whether they can be good enough to be useful in some way, and if we can ignore the flaws.

Interestingly, some flaws have come to be accepted as the “right” way. The classic example is that movies are shot at 24 hz. This is a very low frame rate–well below the capabilities of our eyes–and the only reason it’s become acceptable is because moviemakers have come to adjust their technique to compensate (low speed pans, etc.), and (more importantly) moviewatchers have simply gotten used to it. The effect has become so strong that we now associate high frame rates (achievable on new HDTVs) with somehow being cheap and nasty, even though the real world itself operates at an “infinite” frame rate. The first thing I did with my 240 hz LCD is disable the smooth motion feature, because it looked somehow “uncinematic.”

So I’m not concerned with any flaws mentioned. Some problems will be fixed over time (the darker images), while others (the focus issue, etc.) will not. We’ll get used to it.