JUNE 1996

Lighting a Sporting Event - An Olympic Challenge

by Bill Klages

In our area of the entertainment field, we are faced with daily creative challenges. Each project boasts its own set of problems, and it is our continued ability to find effective and imaginative solutions to these problems that results in award-winning productions and critical acclaim for our Guild members. Still, I had never associated the term “creative” or “challenging“ with the task of lighting a basketball game. But this assignment had a set of unique and fascinating challenges all its own.

The problem is a simple one: provide lighting suitable for television broadcast for the Gymnastic and Basketball Olympic competitions in the Georgia Dome in Atlanta this summer.

The Georgia Dome was built in 1992 to provide a general-purpose enclosed space large enough for a football game. As with all large arena designs, the most difficult design problem is always the means by which the roof is supported. The Georgia Dome, which seats 71,500 for a football event, or a tractor pull for that matter, is covered with a double layer of a Teflon coated fabric. The area of the roof is more than 350,000 square feet. The roof is translucent. In the middle of a sunny summer day in Atlanta, the floor of the arena is lighted to 300 foot-candles.

An ingenious roof support system was designed by Weidinger Associates, a noted authority on the structural design of cable supported roofs. Utilizing a principle called "tensigrity", invented by Kenneth Snelson and championed by the visionary Buckminster Fuller, the roof is composed of three concentric oval cable assemblies, vertical columns in compression held in position by a system of three cable spreaders. These cables transfer the roof’s forces to the outside walls and columns of the building. This unique roof structure is shown in enclosed photograph. Bear in mind that the three oval support cables are actually assemblies of four 4-inch diameter high-strength cables and actually have catwalks attached to these assemblies around the entire perimeter of each oval!

Because of its design, the roof is quite dynamic and can actually shift its lateral position as much as three feet under a high wind! It is the deformation under non-symmetrical imposed loads that is a major concern of the roof designers.

The two most popular events of the summer Olympics for North Americans are Gymnastics and Basketball. Realizing the popularity of these events, the Olympics governing body placed these two events in the largest possible venue, the Georgia Dome. However, since there is some overlap between these two competitions, the arena was divided into two sections by a curtain, about 80 feet high, so that both events can be scheduled during the same day, although not during the same time.

The first problem should be apparent. The installed house system for the lighting of the arena is designed for full field events not for two cross-wise fields of play. Under this setup, problems are created for all event systems: sound reinforcement, audience handling, and so on, as they were designed for one event using the full length of the arena.

The need for a new, temporary lighting system for gymnastics and basketball competitions had now been generated. I was contacted by David Crookham of MUSCO Mobile Lighting to act as a lighting consultant for the project. (Yes, they are the same company that supplies the mobile lighting trucks to light those large night-time shots). I suggested two very straightforward systems of aluminum trussing, the type used so universally for concert tours. These two truss systems, one rather extensive since it would provide lighting for the nearly 30,000 square foot gymnastics field of play and the smaller system for basketball, would be suspended from the roof structure at about 80 feet above the floor, this height being necessary to clear audience sight-lines. From this truss we would suspend the lighting instruments as well as additional speakers, overhead cameras, a track-mounted camera that travels 250 feet, decorations, flags, additional scoreboards, etc.

Another problem arose. During daytime athletic events that have been televised in arenas with translucent roofs the brightness of the roof has been a serious detriment to the photographic quality, silhouetting the competitors on many of the low camera viewpoints. Examples of this problem were experienced in the gymnastic events from Barcelona and Seoul. In Seoul, the roof was painted. Barcelona had no solution and broadcasters proclaimed, "this will never happen again." In the case of the Georgia Dome, paint was ruled out early because of damage to the fabric that was used in the roof of the Dome. Blocking the light from within the dome turned out to be the only practical method. This is achieved by using over 160 triangular pieces of opaque vinyl awning material, inherently light-weight and flame resistant.

This is where the plot thickens. The total load that was to be placed upon the dome roof, although not excessive for more conventional structures, was far in excess of what the roof could safely support by a factor of 2!

There was no turning back at this point. A viable solution had to be determined that will accomplish all the requirements for holding the two competitions, but meet the very restrictive weight limitations imposed by the building's structure.

It became necessary to rethink the original overhead support system. The first thing to be questioned was the use of suspended trusses. At the suggestion of our rigging consultant, we re-designed the rigging method to suspend each element by means of wire cables, thus lowering our weight load. Although this would increase the complexity as well as the cost of installation, it was the only realistic course of action other than moving to another venue (not an option).

Enter now the places of attachment for the black-out shroud. The manner in which all overhead equipment was suspended in the dome was from the upper "nodes" of the roof which are at the top of the suspended compression columns. With our proposed hanging method, if we attached to these points alone, we would create a spider web of cable that would be so complex, we would never be able to sort it out and install.

An appeal to the engineers of the dome resulted in an accommodation that would allow attachment to the oval cables utilizing the catwalk structure as the actual attachment point. The only restriction being that we pay particular attention to distribute our applied loads as evenly as possible over the area of the structure.

The enclosed drawing shows what was to become the acceptable solution. Some of the major elements that are to be suspended are noted.

And now, the lighting plan. The basic lighting unit is a 1500-watt metal halide unit manufactured by MUSCO Lighting, the parent organization of MUSCO Mobile Lighting. Typically, it is a floodlight unit that is available in a range of beam angles to accommodate the lamp throw distance. Since it is a non-lensed instrument, its pattern is soft-edged. The specifications of the Olympic Committee call for 2000 lux (approximately 200 foot-candles) on the competition areas of gymnastics and 1400 lux for basketball. These high levels are to accommodate the longer lenses used on the cameras televising these events. Recognizing the economics involved in specifying broader spectrum lighting instruments as HMI sources, the color rendering index of 65 for this lamp type is acceptable. The color temperature of these lamps is approximately 4000K.

A major consideration is the direction and quality of the lighting. Nearly all competition committees would like a shadowless illumination from directly overhead. This is directly opposed to the lighting preference of the broadcaster, who would also like even illumination, but in the horizontal direction rather than vertical. In addition, it is desirable that there be as little light on the audience as possible to add to the drama of the foreground. Another major requirement of the competition committees is that there be no lights directly in the eyes of the athletes when positioned for critical tasks - on the uneven bars, rings, and so on. So positioning and focus of the instruments become quite critical to satisfy all of these considerations. Compromises from both ends become necessary. Certain aspects, such as competitor's comfort, take priority over other considerations.

Returning to the lighting equipment. For gymnastics, 8 of the individual units are mounted in groups of 4 on two light bars. Even illumination of the field of play for all angles is necessary. A total of 184 units are to be utilized to obtain this illumination. Focus of these units and the resulting distribution of the lighting is done by means of a proprietary computer program used by MUSCO for their permanent lighting installations. Similarly, the basketball set-up will use 144 units in groups of 12, which is the standard lighting set-up devised by MUSCO and approved by the NBA. Both sets of units will be pre-focused prior to shipment as determined by the computer program. It is expected that only minor adjustment will be necessary after installation.

It is interesting to note that it would have been an impossible task to provide the structural engineers the forces on each of our cables without the use of CAD. (My previous article for last year’s lighting issue was an introduction to the use of CAD in production lighting design). I was able to able to easily extract the direction of these forces from a 3D wire frame drawing of which the enclosed drawing is a much simplified version. The data is available from the drawing’s data base by merely picking the cable and reading the vectorial components. A spreadsheet did the actual calculations. If this information had to obtained manually it would probably have taken till the next summer Olympics.

The next step will be installation in June. The final, and most important phase will be the actual events. Let’s hope that you will never notice the lighting. If that be the case, our work has been a success.