The only time that I have felt it was worth it was Avatar and even then I wanted to yank the damn thick-rimmed glasses off my face every 3 minutes.
The good Avatar 3D experience happened because James Cameron is a technically savvy director, and thus the 3D aspect of Avatar was technically well executed. When done right it allows the viewer to more seamlessly enjoy a 3D film. Done poorly and all it does is get in the way. One of the reasons I'm not digging it is that many of the stereoscopic movies have been made 3D after they were shot, which can cause heaps of distractions in the final product. Even if the film was originally shot 3D it takes someone knowledgeable in the field to make it effective. Decisions on convergence between the left and right eyes are just as much a part of the visual storytelling as lens choices, lighting, rack focusing, etc. If you overlook that you get a sloppy 3D experience.
The problem with fake 3DThe process of making a movie 3D after it was shot is a complicated and time consuming process but can be somewhat convincing. The problem is it will never reflect the same results as if you were filming using two cameras, simultaneously, from slightly different perspectives. Endless rotoscoping provides layers that can be separated to fake a different perspective for the second eye, but that's what it looks like, layers. So yes, you can push things away and pull things forward and enhance the depth, but the content within each layer has no depth. We use our eyes everyday and whether you know the geek stuff or not it's just not what we are used to seeing. The stereo technicians involved in bringing the images to us in 3D in the best possible way have their hands tied in some ways, they're not often working with two true perspectives.
The problem is it's expensive and difficult to do it right. Double the camera gear means double the footage and often doubling the camera crew. It also doubles much of the visual effects work as you have to render everything twice. A lot of the old gags we once used to do our "movie magic" no longer work in stereo films.
But what you get is the real thing, a true stereo view of everything in the frame. Just like a director or cinematographer chooses to focus the camera to direct the viewers eye you must make the same decisions in 3D to direct the convergence of the two eyes. Not doing this right (or having to do it with a faked perspective in the second eye) is like overlooking composition or sound design, it's crummy movie making.
Avatar hit this right. They shot it stereo and kept all the depth within screen like it was a window into another world and never tried to wow you with shoving stuff into the theater at you. When you bring elements of the image into the room you run into the problem of the edge of frame cropping the content. During the end titles for Alice In Wonderland they created a false black edge to the screen so that when content did break frame and bring things into the theater they weren't cut off. But this isn't an option for the duration of the movie unless you're willing to give up valuable screen space. IMAX helps relieve this by filling your field of view but we are all far from having IMAX theaters at every cinema and you still have a limited view from within the frame of the glasses.
Milking the 3D cowThis problem will get even worse when you all get sucked into buying a 3D TV for your living room where the size of the screen fills even less of your view. And now there's talk on the rumor mill of re-releasing Titanic in 3D? Watch out for a flood of classics being shoved down the fake stereoscopic pipeline and into your Blu-ray player for an extra $10. Hopefully Cameron will continue to help set a higher standard.
And there's the final nail in this absurd 3D show: The eyeglasses. Simply, watching a $200+ million dollar movie with $.03 crappy plastic glasses is just silly. They are not only optically poor but they take almost a full stop of light out of the image. That's almost half the amount of light! None of the prints or projectors I have seen 3D movies in properly compensate to counteract that loss of light. When I saw Alice In Wonderland at one of the industry screenings—where you think it would be dialed in just right—the image was still painfully dark. The situation in a majority of theaters out there is as bad or worse. - Alexander Murphy (io9)