5
THE DESIGN STAGE

Your first concert design will probably be for a local promoter, a college, or a local band. This stage of building a reputation and, more importantly, building confidence in yourself usually puts you into the type of show where the artist has no touring equipment and probably has a very sketchy rider that gives a stage plan (probably nothing like what they are currently touring), and maybe a basic color chart. You may not even get to “call” the headliner, only the opening act.

So, what are you to do? First, go to the promoter and find out how much can be spent on equipment rental. Second, consider the facility where you will be doing the show. Does it have the required (or hoped for) number of follow spots? If not, it will be a big chunk out of your budget to rent them and pay the operators.

The best design for a show like this is a very simple, straightforward one; it may also be the safest, but that is secondary. Three or four colors for each of the backlight and sidelight circuits may seem too easy, but that is what 80% of the local concerts get. If you are sure the star will stay at the microphone, add some backlight specials to separate and bring him out from the band. (Later I will show a basic plan for most back truss and side tower-type lighting rigs that would tour with a jazz or country artist, even many rock bands. I have seen many such simple plans on the road that are used very creatively.

The truth is, if you pick colors correctly, you can mix and get just about any color you desire. The next stage is to add specials as needed, money or dimming permitting. Too often designers get so hung up with big that they forget clarity in design. In addition, a wide range of special effects and projections could be added, but these are beyond the type of show we are discussing here.

Okay, let's take a step back, because I am sure you just said, “What about moving luminaires?” Be very careful here. First, they will take up a big part of your budget. Second, ask yourself: “Will I really have time to program looks?” This is not intended to discourage you but to make you pause for a minute. Yes, you want to impress the promoter, club owner, and even the band … but at what price? If you end up not having the time to program, the show will suffer and you may look foolish in the eyes of the exact people you were trying to impress. It may be wise to do your first show for a new client very simply and put your full concentration on doing a lot with a little. That often impresses more than a lot that does little.

Many designers who are touring with bands that do not travel with equipment will carry a computer disc with preprogrammed looks that can be modified for each venue. A few will be able to get the artist to pay for them to bring along a lighting console that has the show in memory, and with some local repatching you can be ready to go. Some will even travel with a small moving luminaire package so they can add them to the house rig and have their program added to the house console.

THE WORKHORSE OF CONCERT LIGHTING

The parabolic aluminized reflector (PAR) type of medium flood (Med) lamp is best for general washes. They come in many sizes and wattages, but generally concerts use the largest and highest wattage PAR-64 (1000 watts). F(N) or very narrow spot (VNSP) lamps are used for special and accent lighting. The PAR-64 and the less used but valuable family of PAR luminaires (see Chapter 18) are the workhorses of conventional luminaires used in concert lighting. Being relatively trouble free and devoid of parts that can jam or break, these units have the most effective, dimmable light source available among the standard theatrical and film luminaires. For 45 years, the PAR lamp has continued to be the most reliable source for “punch” ligh ting.

The efficiency and type of beam spreads available for the PAR-64 luminaire should be viewed in a couple of ways. There seems to be a preoccupation with efficiency because the availability of a sufficiently large power service can often be a problem. If you are going into an old theatre or college gym, access to auxiliary power can be a headache; consequently, you want as much light as you can get for as little power draw as possible. The PAR fits this bill best of all. The sealed-beam lamps offer a range of beam spreads that give you coverage from very narrow to wide flood fields. These lamps can give you concentrated beams of light that will project even dense color a great distance. for example, compare the beam spread at a 30-foot throw between the very narrow lamp'3.7 × 6.4 feet'and the medium flood lamp'6.5 × 15.5 feet'as measured at 50% intensity. While on the subject, those same 1-kW lamps produce 560 fc and 150 fc, respectively, at that distance, compared to a 1-kW Fresnel, which can only produce 195 fc at spot and 40 fc at flood focus at the same distance.

AIR LIGHT

Air light, often referred to as air graphics, became an increasingly prevalent term in the late 1970s and early 1980s. There was an undeclared race among touring rock bands to reach new records for how many trucks they had out on tours and how many of those trucks carried truss, lights, and staging. At the time, Van Halen proudly claimed that they carried 1300 lights, including every PAR light bulb and each one on 8-light audience blinders. Air graphics are possible when there is a lot of haze in the air. This contained smoke gives narrow-beam PARs the air surface necessary to trace a light beam from 16 to 24 feet above the stage floor, but without physical staging to light up or reflect light. Smoking was still allowed, and smoke machines or hazers were not carried until the mid-1980s. Big arena tours sought to achieve a smoky club atmosphere, and some lighting designers even requested that a facility's powerful air-conditioning units be shut off just before a show so fat beams of light could be seen. As a way to avoid having to mount more and more rows of lights to illuminate the performers or staging, air light became a practical way to animate lighting scene changes using color from different beam angles and create movement in the air. Designers arranged banks of light purely for effect, and air graphics became a large part of the overall design of many tours and television specials. By the time moving luminaires came along in the early 1980s, air graphics had become a finely tuned craft, and moving beams through the air added greatly to the excitement that air light creates (Figure 5.1).

MOVING LIGHTS (LUMINAIRES)

A big change in the way we speak of theatrical lights has occurred recently. For years, people referred to them as anything from lamps to fixtures to lights. The term commonly used today for lights that remotely change position is luminaire. This is a word that Vari*Lite originally coined for their computer-controlled lights, and it has now entered into the lexicon of the entertainment business. Recently, the Essential Skills for the Entertainment Technician Committee of the Entertainment Services Technology Association (ESTA; see certification discussion in Chapter 2) adopted the word to replace fixture to define all fixtures, not just moving lights. As of this writing, the industry has not fully embraced this change for a long standing term, but we believe with the Committee's endorsement the term will start to be used by younger technicians and designers.

If you have a moving luminaire package, you might be well served by using them more for repositioning and color or pattern changes than for flash or

to add sizzle at the end of a song or the band's bows. I once saw a Bruce Springsteen concert designed by Jeff Ravitz. I had been told that the lighting package was all moving luminaires. But, as I watched the show, I never saw a luminaire move. I actually thought the program had somehow malfunctioned. Then, as Bruce was leaving the stage after the last number, the lighting exploded in a riot of color and movement. There was no way the audience would not applaud and bring him back, even if he wasn't “The Boss.” Jeff had used the moving luminaires to change color, pattern, and position when they were not on so each song had a different look with a minimum of luminaires, and he saved the big bang for the end. That showed great showmanship on his part.

Computer-controlled moving luminaires are everywhere. At last count, there were over 35 manufacturer's producing club and touring models worldwide.

OTHER LUMINAIRE CHOICES

Other available choices are beam projectors, ellipsoidals'Lekos, ellipsoidal reflector spotlights (ERSs), or, as the Australian, English, and European companies call them, profile spots (see Chapter 18). Fresnels can also come into play, as well as the various types of striplights and luminaires designed around multiple PAR lamps. Recently, light-emitting diode (LED) light sources have given us a whole new category of lighting, as have the digital luminaire instruments that can show images as well as colors. The beam projector, also an open-faced luminaire, does just about the same job as the PAR-64, but with a very low efficiency factor (see Chapter 18).

The ERS or ellipsoidal has not been given the status on tour that it enjoys in the theatre, but more and more we are seeing it being employed for concert lighting. Some people consider the author to be this luminaire's biggest booster. I once did a tour with over 180 ellipsoidals and only 4 PAR-64 luminaires. This does require a high degree of confidence in your design; however, this is true only when you have a show in which you are not confident that the talent will hit the rehearsed marks. Artists who cannot hit marks do more than hurt your design; they are wasting their money. If the effect cannot be seen because of their inability to be consistent in their movements, then the luminaires are not needed and are just so much excess baggage. Electronic Theatre Controls (ETC), Inc., was the first company to revolutionize Mercury (Hg) the standard ellipsoidal in 1992. Strand Lighting and others followed later with their own versions. ETC's concept coupled a new lens design with a new lamp design. The lens was sharper, and it had fewer aberrations around the edge and cleaner shutters. Moving luminaires can also project patterns (gobos), or you can choose from a variety of lens spreads or even add an iris to narrow the beam. So, consider the cost difference. If you want the pattern to be used multiple times, why tie up an expensive moving luminaire?

The Fresnel luminaire doesn't have a great following in the concert market because of its weight and limited efficiency. Other luminaires include the film Mini-Brute, an early application of the PAR lamp designed for broad fill lighting for film and location shooting. Mercury medium-arc iodide (HMI) Fresnel luminaires do find special uses from time to time. Generally, you will find that concert equipment manufacturers have produced their own designs for grouping PAR-36 luminaires into single luminaires usually used as audience lights (see Chapter 18). Another variation of audience lights, created by Doug Brant and Justin Collie of Artfag LLC, has a strobe built in; it is called the Litepod and is manufactured by Wybron, Inc. (see Chapter 18).

In the final design, virtually any luminaire can be used if the designer has the vision to see what effects it can produce and can use it accordingly. Always keep in mind that the instrument or effect must work night after night. Nothing is worse than when an effect the artist comes to expect does not work.

PLACEMENT OF LUMINAIRES

Concert lighting reverses basic light direction used in theatre. Whereas theatre puts great importance on frontlight and least on backlight, concerts completely reverse this concept. Two factors are responsible for this. First, there is little or no possibility of consistently getting a balcony or front-of-house (FOH) position to use for a concert tour in 30 or 40 found spaces (spaces used but not specifically designed as performance areas). Second, lighting in concerts is viewed as providing effects and accents rather than the theatrical function of facial visibility. Thus, the idea is to produce all the front light with one or two follow spots and to focus the fixed lighting on providing special effects and complementary colors for stage washes, breakup patterns, and backlight to surround the singer or players with color.

This use of backlight is known as accent lighting, to distinguish it from the theatrical style. Light is concentrated at strategic points on the stage to punctuate the music with deep colors. This method of lighting truly fits the maxim:

It's not where you put the light; it's where you don't put the light that counts.

Keeping this in mind during your designing efforts will serve you well in not overdoing the design. Too many shows load in 200 luminaires when 100 will do. I had a problem with a group that wanted me to add more luminaires to the tour because they were cutting back on the set. The logic was that if they had less scenery, more luminaires could fill in the void. Wrong. You cannot light what is not there, except when using air light. I already had an adequate number of luminaires in the plot to light the band and didn't desire anything more except effects and projections, but they had just eliminated the things I needed as surfaces for projection.

The quantity and placement of luminaires must be directly related to the placement of band and vocals. It is unreasonable for a manager to request 80 lamps, or 200 lamps, for his client; my standard reply is, “Okay, I will use that for the budget figure, but I must know more about the artist's needs.” I see no point in renting 80 (or 200) lamps and then trying to figure out what to do with them, but I have been put in this position on several occasions.

The most effective designs I have seen used fewer luminaires. The timing of the cues, the color selection, and the organization of effects were far more powerful than adding additional luminaires would have been. Good design in any field is not based on quantity.

COLOR

In my own designs I try to think in terms of colors, not quantity of luminaires, before I begin to draw a light plot. What I am trying to picture in my mind are looks, planned patterns of light direction and color that will be used one or more times during the show. The term looks started out as a television term, but now most designers use it to describe the patterns created by the lighting.

Primary and secondary colors are generally best. For a general plot, try for four colors as sidelight and five colors plus white for backlight on the lead artist. Bands usually get four colors for backwashes and three colors for sidelight, plus two back specials' one warm and one cool color, such as Lee filters #105 (orange) and #137 (special lavender)'to accent their solos. I prefer not to use a follow spot every time a short guitar break happens. A nice hot backlight stabbing through the darkness, while dousing the follow spot on the singer, can be very effective. When I am able to get front specials into the design, I add a warm special and a cool special to each solo player, plus at least two general front or top band washes.

How different colors affect the audience's visual interpretation of the music is key to how a designer interprets the music. You are strongly advised to read one of the many excellent theatre lighting textbooks in print for a full discussion of light and the human eye. My favorite book on the specific subject of how light is received and interpreted is The Beauty of Light,¹ by Ben Bova, a physicist, although it is currently out of print.

CIRCUITING AND DIMMING

The luminaire complement is tied to the dimming available, except with HMI luminaires. It is fashionable for designers not to concern themselves with such trivial matters. After all, you were probably taught to leave that to your master electrician or gaffer; however, reality dictates that the availability of equipment most often forces you to pick from a choice of dimmer packages, usually in groups of six channels of a particular wattage: 2.4 kW or 6 kW. Not many 3.6-kW, 8-kW, or 12-kW dimmers are found on the road. The 1-kW dimmers are usually packaged in larger groups, a common quantity being 72 per rack (see Chapter 12). Always leave some dimmers with unused capacity so that, if and when you have a failure, you can gang channels. Better yet, leave two of your largest capacity dimmers as spares in the first place.

LAYERING

Besides basic position and angle, look to another idea for most of your visuals: layering. This is the process that creates depth and separation by using different shades or saturations of color. Except for effects, I rarely bathe the stage in a single color except between songs. That gives no visual depth. With a conscious consideration of color, coupled with intensity, you not only can direct the audience's attention to a specific part of the stage but you can also put the total stage into perspective. Too often, I see shows that rely totally on the follow spot, with its dramatic shaft of bright light, to accomplish this task. That is the easy but boring way out. The source of light is important, but so are the hue and tone of the colors used on stage. Many readers will believe they have to put a lot of different colors on the stage all at once, but for a more sophisticated effect you can layer in a single color by hue variation. Also, do not forget that the absence of light also contributes to the overall effect.

I first realized how important this idea can be during my early television lighting assignments. In video, the camera cannot show depth of field; lighting directors must accentuate depth by means of backlight and differences in intensity between the foreground and the background. That same approach can be applied to concerts when the audience can be as far away as 150 feet from the stage. In theatre, layering can be applied to subtly draw attention to a particular part of the stage. Here, again, not just the choice of luminaires and angle but also the mix of colors you use can make a better, clearerde sign.

LAYOUT AND SYMBOLS

Lest anyone think that with the drawing of the light plot the design is finished, let me talk about the next step in my approach to design. I have often marveled at beautiful computer-aided drawing (CAD) light plots, only to be disappointed by the execution of the show. On the other hand, I have often seen light plots scribbled on graph paper or the proverbial envelope that are exciting and show great style; however, even when circumstances have made proper preparation impossible, the additional effort and time wasted explaining such crudely drawn plots cannot be defended. The designer owes it to the technicians to give clearly understood and accurate instructions, and they are best conveyed by the properly drawn light plot. Figure 5.2 provides an example of a concert light plot for a festival; it doesn't follow the USA layout rules but is quite effective for touring designs.

As you study theatrical lighting, it will become apparent that there are several schools of thought regarding technique. Some styles are created by teachers at a particular institution of learning, or you might learn the so-called Broadway method perpetuated by the USA/IATSE union examination. The Broadway style prevails, but some West Coast designers have made changes that reflect a more open thinking. (Keep in mind that if you do wish to practice your craft on Broadway you will need to learn it as required for the exam.) Add in the distinctive style of the British school of design that has been injected into the United States and you have an evolving system that no one can agree upon. The United States Institute for Theatre Technology (USITT) took years to agree on standard symbols for lighting instruments.

Many concert and even successful theatre designers have had no formal schooling (see Chapter 23, where four top designers talk about their educations). Everyone will either succeed or fail based on what they put forth; no one method works for everyone. This is a highly creative field that always awards style and ingenuity. Partly because a portion of these designers are not formally trained and therefore don't know the established rules, they tend to simplify the plot so anyone can understand the color, circuit, and control channels at a glance. The major differences between the two styles of drawing (the traditional versus the modern) can be categorized as:

1. Templates'The traditional method uses both top and side symbols, while concert designers use only top symbols or even simple circles.
2. Electrical hookup chart'Traditionally, this chart is similar to electrical engineering drawings, where a line is drawn joining all luminaires of a circuit. Concert designers tend to use a number inside a symbol to represent the patching.
3. Presentation'The East Coast, or more traditional, method uses separate sheets of paper for the many different details needed to complete the design. The concert and Las Vegas approach is to include all the information on one sheet.

Over the years, I have evolved a method I believe is even clearer. Some variation of this method can now be seen on many concert lighting plots. The light plot shown in Figure 5.3 of a 2008 REO Speedwagon tour has all the information on one sheet that is needed to complete the color and hanging of the show.

I have always had trouble printing numbers clearly on drawings, especially when trying to get the color number, circuit number, and control channel number all in the same space. Although a computer drafting program eliminates this issue, a move toward adding more symbols to the drawing is founded on an idea used by Len Rader, who for many years was the head electrician at the MGM Grand Hotel in Las Vegas. Every light plot that came to him was different, and he said a lot of time was wasted trying to get the crew to understand what the plot represented. So, he started redrawing the plots and keeping them on file so that when the artist returned the load-in was much simpler. On one sheet, he had the circuits, dimmer assignments, and color in a form that everyone on his crew could understand. I adapted his form, which I found easy to understand, and I began using this style all over the world with great success. The plot shown in Figure 5.4 is from a Las Vegas show with Smokey Robinson.

The rectangle (symbol for circuit number) behind the luminaire symbol is blank. When the show is not touring with dimmers, it must be left up to the house to assign their dimmers. Existing house circuits are assigned by staff electricians to best facilitate the hang in a particular house. Luminaires are pointed in the desired direction of focus rather than straight

side-by-side, as the USA exam and the more traditional method require. The 5-foot marks allow for a quick reference to luminaire placement along the pipe.

As mentioned earlier, computer drafting programs have enhanced the clarity of these drawings. Many CAD programs are available. Some are designed specifically for theatre, others for concerts and event production or even architecture. VectorWorks by Nemetschek, North America, Inc., is without a doubt the most popular software among Broadway, theatre, and concert designers. Although you will develop a favorite, all such programs have a common link. The work can be changed time and time again without starting over. This has been a boom to designers who need to make several versions of a tour plot. A fuller discussion of CAD programs is presented in Chapter 21.

HANGING

The final step in your design is not deciding whether to mount the luminaires on a pipe or on a prerigged truss. What looked good on paper may be junk in the air. As the designer, you not only must work closely with the supplier to ensure accurate reproduction of the design but must also be open to suggestions concerning changes that will improve the repeatability, packaging, and focus during the tour. If it is a one-off gig, the access to luminaires must be well thought out because of scenery or band placement. It will be too late once the load-in starts to try to solve a major problem. It might be wise to use a truss so the luminaires can be focused by someone walking or crawling on them (with the proper fall protection

system in place; see Chapter 9). Restrictions as to circuit availability, drapery obstruction, and trim height must all be considered well in advance. I never leave the theatre during load-in on a one-nighter. Designers not attentive during rigging do a great disservice to themselves and the crew and show a lack of respect for the crew's efforts on behalf of the show.

Often the house stagehands will have suggestions that will help simplify the rigging and focus. It is like hunting or fishing in that the locals know the woods and best fishing holes. The designer must keep an open mind to suggestions and not become defensive. It not only helps to have the crew feel part of the show because you listen to their ideas but also shows your good sense to know that someone else can look at the problem and possibly come up with a better solution.

SAMPLE LIGHT PLOT

The light plot shown in Figure 5.5 illustrates a typical rock & roll band setup. It is made up of all conventional lighting luminaires and no moving luminaires. Replace the keyboards with a steel guitar, and you have a country band. This could even be a jazz group. The back truss and sidelight tree design is the starting point for all concert design. Heavy backlight is the trademark of concert lighting.

The band backlight washes could be split so the drummer is separated, as he has no backlight specials. Some people split the sidelight left and right so they can have, for example, a red sidelight from stage left and an amber color from stage right. The real controlling factor is the number of dimmers available.

A more ideal control of these luminaires would be

• 4 band backlight washes (4 luminaires each)
• 4 drummer specials (1 luminaire each)
• 6 band specials (1 luminaire each)
• 6 lead-singer backlight specials (1 luminaire each)
• 8 band sidelight washes (2 luminaires each)
• 8 lead-singer sidelight washes (2 luminaires each)
• 36 total of channels of control

That quantity hits the nail on the head. Most consoles come in 24, 36, 48, 60, 72, or 96 channels of control. I insist on spare dimmers and control channels on the road. That way you can adjust at the last minute if the failure of a dimmer or a control channel occurs. I also make sure I have firmly fixed in my mind, well in advance of the tour, what control I could give up in order to solve a problem.

Preparation is critical. Using this plot as an example, first I would give up sidelight circuits, and then I would gang drummer backlight to band washes. In either case, the dimmer capacity must be high enough to accept this additional load, and advance planning can cover that point. Always have a few dimmers that can accept additional loads. If some moving luminaires were added to this plot, you should already have thought out what they might be able to compensate for if you were to lose a critical conventional luminaire.

The colors I would select change, depending on whether the lead singer is male or female and even whether they are black, brown, or white. Without going into the basic theory of color as it applies to theatrical lighting, it should be easily understood that any color (actually the absence of a portion of the visible light spectrum) projected onto a color will affect how the human eye perceives that color. Therefore, the designer must be sensitive to skin tone to most effectively illuminate the artist. The following color chart would be an acceptable starting point for most acts. Note that I have not designated specific color media. At this point, we are more concerned with the broader picture; exact color numbers are not yet important:

• Band and drum backlight
  • Red
  • Blue
  • Lemon
  • Green
• Band backlight specials
  • Lightpink or lemon
  • Lavender or sunrise pink
• Band sidelight
  • Amber
  • Blue
  • Blue/green
  • Lavender
• Lead-singer backlight
  • Red
  • Lemon
  • Lightblue
  • Lavender
  • Magenta
  • No color
• Lead-singer sidelight
  • Red
  • Amber
  • Blue
  • Lavender
  • No color

COLOR CHANGERS, MOVING LUMINAIRE, AND EFFECTS

A few color changers (the scrolling type can give 6 to 32 colors) can make even the simplest plot more flexible for an advanced designer. (Color changers are discussed further in Chapter 18.) The possible combinations that this multiplicity of color brings to the design would be much more advantageous on the road than the increased quantity of luminaires and dimming that would be required to achieve the same effects. Remember that shipping space is critical.

Moving luminaire and truss-mounted follow spots could also add to the flexibility of the system without increasing the physical truss configuration. The pizzazz that is possible from even a simple layout can be used over and over again. Add the toys only after you have mastered the straightforward plot or you might get in over your head. Complexity can add confusion, and the time it might take you to make a decision can spell disaster.

VARIABLES

Lighting fascinates me because it never looks the same twice, even with the reliability of a computer console. The atmosphere of the room changes from hall to hall, and people's perceptions are slightly altered. Smoke in a night club or at concerts makes the light stand out more. Light from exit signs or candles on the tables can change the darkness level (black level, in TV parlance) from show to show.

Other variables are voltage to the lamps and changes in position and elevation. When you move the show from one hall to another, the voltage could change. Not many halls have exactly 120 volts at the input service'it often varies between 108 and 120 volts'and then when dimmers are added they will drop another 2 to 4 volts on the output side. String 50 to 100 feet of portable cable to the lamp, and it is rare to have 120 volts at the lamp filament. Therefore, the color temperature changes each day, and the color won't be exactly as planned. With many colors, this will mean visibly altered colors.

Moving the trusses or truss upstage or downstage a couple of feet makes a difference in the angle at which the light will strike the performers; this alters the shading and contrast of your lighting. Another variable is in the follow spot positions from hall to hall. Are they straight on or at a 45-degree angle to the artist? Every variable will make a difference from show to show and alternate plans must be considered in advance.

Twelve designers can take the example in Figure 5.5 and create 100 different looks. That excites me,

and I think concert lighting releases the same creative magination as theatre. We must take 50 artists, all of whom perform with similar staging, and make each look different.

One final word of advice: Experiment, experiment, experiment. I do, even with a show that is already touring. If I am running the board, I may try different things. If you are not sure how your client will react to unannounced changes, you might want to play with the changes at sound check to get a reaction before adding them into the show. Sometimes it is better, sometimes it is a toss-up, and often it is worse than my first idea. But, I still try and I will keep on trying to bring clarity and definition to my design.

MORE COMPLEX DESIGNS

After you become proficient at a simple, straightforward plot, you can move on to some more grandiose designs. This field of design loves the outrageous. The creative freedom begins with the structures you design. Trusses come in all lengths, shapes, and load capacities. At this point, simply think of geometric patterns and designs. The examples in Figure 5.6 are only a few basic ideas for possible grids. More than making a pretty design, the objective is to choose light angles that create mood and drama.

Although there is the practical limitation of load capacity, I have seen trusses that defy structural logic. In Chapter 13, we provide the technical information required to help you decide on a final truss layout. I would caution that before becoming married to a design you consult with a rigger or at least the lighting supplier for advice on how your dream can be accomplished. However, at this pure design phase of our discussion, you can see how the structures become a real element of the look. Keep in mind that, in almost all of the touring systems, the structures will be in view of the audience. The layout of the structures can be both functional and an aesthetic element of your show.

1 Ben Bova, The Beauty of Light, John Wiley & Sons, New York, 1988.