Digital 3D - In a Theatre Near You?

by Michael Karagosian
©2005 Karagosian MacCalla Partners, all rights reserved worldwide
Published in the August 2005 issue of INS Asia Magazine

Much has been accomplished towards perfecting digital image projection for the cinema, but far less has been accomplished in demonstrating new digital capabilities that can improve box office revenue. While electronic advertising has been demonstrated to be a significant source of new revenue, it does not require the high quality, expensive projection systems that are characteristic of digital cinema. The first breakthrough in demonstrating a new and marketable capability for digital cinema was presented in March of this year at ShoWest with digitally projected 3D (stereoscopic) content.

3D has captured the imagination of filmmakers since the early days of the medium. The earliest 3D piece this author knows of was a segment from Jim the Penguin in 1915. However, 3D has always remained a novelty, never transitioning into a wide-spread standard format for film.

There are major drawbacks with 3D that have kept it from becoming a mainstream format. It is difficult to capture 3D images, requiring special camera rigs which can be difficult to monitor for their stereoscopic effect. 3D capture can introduce artificial misalignments between left and right images that strain vision and cause headaches for the viewer. 3D capture is also challenging for the filmmaker who wishes to maintain a particular dimensional perspective among related shots. On the exhibition side, it has been difficult to project 3D images in the theatre with high quality. Some have achieved this, as IMAX has with its well-known 3D projection. While several methods have been tried in mainstream cinema, all are faulted for either lacking in quality or being difficult to implement.

Major Film Directors at ShoWest 2005 Ready for 3D
from left to right: George Lucas, Robert Zemeckis, Randal Kleiser, Robert Rodriguez, James Cameron
photo courtesy of Boyd MacNaughton of NuVision

Despite these drawbacks, there are filmmakers today who are passionate about 3D and have invested significant effort to employ it in the telling of their stories. Among these are James Cameron ( Ghosts of the Abyss and Aliens of the Deep), Robert Rodriguez ( Spy Kids 3D - Game Over and Shark Boy and Lava Girl), and Robert Zemeckis ( Polar Express). Disney recently made history by announcing its plan to release Chicken Little later this year in 3D on digital screens. These filmmakers based their 3D production on either live stereoscopic image capture, computer-generated stereoscopic graphics, or a combination of both. The presentation of their films has taken place in different ways as well. Dual projectors are often used in large format presentations. In these installations, the viewer wears "active" 3D shutter glasses that synchronize with the projection system, ensuring that each eye will only see images from one projector. For 35mm installations, an "over-and-under" method has been used requiring only a single projector with a special lens. A more common 35mm projection technique utilizes an anaglyph format where left images are colored differently than right images. In the anaglyph format, the viewer wears glasses having the appropriate color filters to insure that each eye only sees the intended image.

While the technology is available and has successfully been used to create 3D versions of computer-generated animation, the challenge of capturing live action in 3D continues to keep it out of the hands of most filmmakers. But that is about to change. For 7 years, a company in the Los Angeles area called In-Three, founded by Michael Kaye, has been working to perfect a technique for converting 2D motion picture images to 3D, using a process named Dimensionalization™. Today, In-Three has been behind a series of private and public demonstrations that has captured the attention of many major filmmakers. It was In-Three's conversion of the opening scenes of Star Wars Episode IV, as well as converted clips from other movies, that caught the attention of exhibitors and press alike at both ShoWest 2005 and (in a private demonstration) Cinema Expo 2005. It was also In-Three's technology that prompted George Lucas to announce his intent to re-release the Star Wars series in 2007 in 3D. Technologies such as Dimensionalization allow filmmakers to create stereoscopic motion picture productions using the 2D tools they are comfortable with.

With 2D-to-3D conversion technology now available to solve the content availability problem, the industry next needs a wide-spread method to display 3D movies in the cinema. Fortunately, this opportunity exists with digital cinema.

There are two 3D projection techniques that have been demonstrated with digital projection. They differ in the need for image pre-processing (versus no image pre-processing), in the need for modification to the projector (versus no modification), in the type of screen used, and in the glasses used.

The format to be employed by Disney with the digital 3D presentation of Chicken Little was developed by Real-D. This format employs the combination of image pre-processing, an LCD-shuttered polarizing filter in front of the projection lens, a silver screen to maintain light polarization, and passive polarized glasses worn by the audience.

The intricacy of this method is well-thought out, but as with all methods, it has good and bad points. A significant advantage of this method is that it minimizes the operational cost of glasses. For the cinema owner, inexpensive glasses will likely make it cheaper to give away the glasses than to collect and clean them for re-use. A complication of this scheme, however, is that the combined optical path presented by the projector LCD-shutter, the silver screen, and the passive glasses introduces a low extinction ratio for the image seen by each eye. This causes an optical cross-talk in the stereoscopic image, which the viewer observes as ghosting. To understand how this artifact occurs, the 3D effect is created by careful displacement of the objects in the images presented to each eye. If one eye sees even a small part of the image meant for the other eye, the attenuated second image will be visible as a ghost of the primary image. To minimize this ghosting effect, Real-D pre-processes the image using a proprietary image subtraction method. Down the road, Real-D plans to implement real-time image processing in the projection booth of the theatre so that this processing is performed after the content is distributed, rather than before. There are also costs which must be considered. The LCD polarized projector-shutter must gate an intense beam of light, potentially shortening its lifetime and requiring early replacement. The high cost of the silver screen must also be taken into account, as they can run as high as $540 per square meter.

Another method for projecting digital 3D has been promoted by NuVision and In-Three. NuVision is a manufacturer of 3D shutter glasses for government, medical, and industrial applications. NuVision partnered with In-Three to develop cinema shutter glasses for 3D exhibition. The method distinguishes itself in that it does not require pre-processing of the 3D image, nor does it require the addition of an LCD shutter filter to the projector, nor does it require an expensive silver screen to maintain polarization of the light. The disadvantage of this method is that that shutter glasses cost significantly more than their polarized, passive counterparts. (NuVision is targeting $30 per pair for a cinema version of its glasses). Because the glasses are too expensive to simply give away, the exhibitor must collect and clean them, introducing additional labor costs. Active shutter glasses may also have a limited lifetime if their battery is embedded, requiring periodic replacement.

Figures are not available for a meaningful cost comparison of the projection methods described. However, it is conceivable that the cost per-show is not significantly different between them, inviting a competitive marketplace.

Even if different methods co-exist for digitally projecting 3D content, there is sufficient commonality between them to pursue useful standards. This would include the distribution file format, the method for delivering 3D streams to the projector, and the meta-data sent to the projector to set it up for presenting 48fps 3D content. Such standards would bring a new level of interoperability to the cinema industry for stereoscopy, enabling the wide-spread projection of 3D motion pictures. This is a goal the industry should pursue.