The Video Image as a Design Tool The idea of using projected or emissive images as part of an overall design - for example, as part of a theatre set or part of an exhibition stand - is not new. Scene projection in the theatre has been with us for centuries. However, the arrival of electronic images has introduced a new range of possibilities, and much greater flexibility. Below are some of these new tools and the challenges they present.

Flat-panel displays Practical and sensibly priced, flat-panel displays are giving designers new freedoms. Liquid crystal displays (LCDs) are suitable for small images (21" diagonal and smaller) and have improved enormously in recent years. Such tools, for example, simplified the realization of 3D Concepts' design for the "Point of View Diner" in the Museum of Tolerance, Los Angeles. In that project, each "jukebox" received its own video-on-demand program from an Electrosonic video server.

However, designers should still evaluate LCDs in terms of color, contrast, and performance on moving images. Plasma display panels (PDPs) are now available up to 50" diagonal in 16:9 aspect ratio. Their emissive nature, and their colorimetry similar to the familiar cathode ray tube (CRT), make them easy to use, and the new second generation products have overcome earlier deficiencies in contrast and brightness.

Image processing Yet designers need to be aware that they must work within the limitations posed by any particular display technology. The way in which PDPs are constructed means that there is no possibility of "tiling" them to produce a large seamless image - and indeed to try and do so would indicate that the wrong technology had been chosen for the project.

Instead, it is necessary to take account of the reality of the display, and actually make a design feature out of the image structure. When the "pyramid" display first appeared in the late 1980s, it required custom image-processing software to achieve the asymmetric image splitting. Today, however, new high resolution image processing equipment is available that can adapt to any display format, regardless of the number of screens, their relative positioning, or the gaps between them.

In the case of a gridded multiple plasma display, the math is relatively simple - it is only necessary to allow a "gap factor" for each mullion; so the "virtual" picture that would occupy the gap in a seamless display is not shown. But things get a little more complicated when screens are of different sizes, and the gaps are irregular. One special trick, for example, is the ability to move an image from one imaging surface to another of a different size, while the moved image window stays the same viewed size.

The use of mixed screen sizes was recently demonstrated to prospective users of the Electrosonic VECTOR[TM] image processing system in Germany. The large center screen was served by a Digital Projection 15SX Lightning projector. The two flanking displays were 2 x 2 DLP[TM] displays from Sim2 Multi-Media, and the two outside displays were 50" PDPs from Pioneer. The whole set was fed from a mixture of nine PAL, NTSC, high definition, and computer sources. Any of the nine incoming images could appear at any size anywhere on the overall canvas. Images could appear in "flying windows" to move around the set.

Back or front projection The problem that affects all kinds of projection and image displays is ensuring that there is sufficient contrast. Equipment manufacturers boast about the number of lumens their product can squirt out, but this is only one factor among many. Recently I encountered an attraction where the designer had chosen to build a white auditorium - white seats, white walls, white ceiling, white floor. Two 10,000-lumen video projectors were used to front-project a specially made film. But it looked completely washed out because of lack of contrast caused by the white walls reflecting the light back onto the screen.

In fact, the investment of $25 in a can of black paint could have solved the problem, and, what's more, could have allowed the use of one single 5,000-lumen projector to give a subjectively much brighter picture than the 20,000-lumen combo. If the white walls are really fundamental to the design, then the only possibility would be to use back projection, where the use of a dark rear-projection screen material means that the scattered light is absorbed, not reflected.

At Vinopolis, a wine exhibition in London, designed by Jasper Jacob Associates, back projection was used in a novel way. Visitors take a ride round Tuscany on a Vespa, and see the image in the windscreen. When nobody is riding, the screen is transparent, a trick achieved by using a polymer-dispersed liquid crystal electrically-activated screen.

While I personally believe that rules are designed to be broken and that progress in design ideas often comes from such rule-breaking, I also suggest that it is important to know what the rules are in the first place. It is somewhat arrogant to behave as if they didn't exist. (In the aforementioned example - name withheld to protect the guilty - an investment in black paint was made!).

Image sources Until recently, most public manifestations of multiple electronic images were video-based. Now there is a tendency to use a mixture of standard video and computer-sourced images. The advent of low-cost video servers has greatly facilitated the realization of some kinds of display, but there is a real demand to improve image quality.

One way of doing this is to take advantage of the arrival of public high definition TV. This has resulted in a huge growth in HD facilities. High definition video can look really stunning, and the cost of equipment for playback only is not expensive. An example of this technique can be seen at the American Museum of Natural History in New York. "Astro Bulletin" is a display with original material generated on computer. For the actual display, a videowall is used to achieve adequate image brightness in the very high ambient light, and the program is played back as a high definition video program. AMNH science bulletins manager Smokey Forester and his team devised complex multiple imagery from a mixture of computer and high definition sources. They then rendered the high resolution program in HD format (usually 1080i) followed by compression to MPEG-2 (high definition). The resulting show is run fully automatically from a low-cost HD server.

Limitations Using multiple projectors and high resolution sources, it is possible to achieve extremely high resolution and an overall image area of any required size. But some applications need big single images from a single projection source. Electronic projection has its limits - at present around 12,000 lumens from a single projector at a resolution of 1,280 x 1,024. When this is simply not enough, it is necessary to go back to film.

At the Amazing Adventures of Spider-Man[TM] attraction in Universal Studios Islands of Adventure, the requirement is to project 3D images 40' x 30' at a minimum resolution of 2,000 x 1,500, but with some material at 4,000 x 3,000. A luminous flux of around 40,000 lumens is needed. So notwithstanding the fact that the original material is computer-generated, the actual projection can only be done by film (at present).

With all our excitement and amazement at what can be done with electronic images, we must always remember that it is the story, not the technology, that counts - and the technologists among us must always advise users on the "appropriate" technology, not the "hot" technology.