9

Studio technical design

 

Introduction

The installation of lighting systems has a major impact on safety. It introduces large mechanical loads to structures. Heavyweight devices are hung over areas which may be populated by the public, artists or technicians. The lighting system introduces electricity to many areas and, particularly when this is on flexible leads feeding equipment, can be a source of danger. Most of the heat generated in the building will probably come from the lights being used. The electrical and mechanical systems installed can maim or even kill if we fool with them. Therefore, there is a necessity to install lighting systems as safely as is humanly possible.

Generally, systems have luminaires in one place and the dimmers that control them in another. Over the years suggestions have been made for the controlling dimmer of a light source to be within the luminaire itself. In the case of the standard arrangement, all that is required from the dimmer to the luminaire, are two wires carrying the live and neutral or the positive and negative. In the case of motorised luminaires, signals in addition to the mains feeds have to be provided. If a luminaire is used with a dimmer mounted within its casing, the mains can be taken either from a radial supply system or from a ring main, but one has to remember that with a large number of luminaires, the ring main conductors become very large indeed, and the weight of the cables will be a problem. Conversely, dimmers traditionally are not the lightest of objects and we suspect that each luminaire would have a reasonable weight addition to its normal configuration. This would then mean the luminaires themselves are getting heavier, consequently they may impose additional loads on structures that are inadequate. By using dimmers within luminaires, a careful approach would have to be made to the protection of the wiring feeding these luminaires, either by the correct fusing or choice of mcbs.

May we make a plea to all architects and end users to contact a reliable lighting consultant before deciding on the shape and size of any new facility. We have both experienced the problem of being called in at a late stage of construction and being presented with a fait accompli, having no regard for the technical requirements.

9.1 Project team

Before discussing the technical aspects of installing lighting systems we have to have a team of people who will be intimately involved with the planning and construction of such systems. Normally on large installations, a ‘project team’ would be formed consisting of senior key personnel. These would comprise the architect who will be responsible for the overall planning of the building installation and its associated services. His major concern will be the construction of a pleasing building or conversion of an existing building, together with the correct installation of any technical plant. He will be aided in his work by a quantity surveyor, who will cost the work and thus enable the architect to make decisions with regard to the budget. One of the main concerns of the architect will be the size of the structure required to support lighting systems together with the weights involved. To solve the structural problems that will arise, a structural engineer will work very closely with the architect, and it is his calculations that will decide the structure of the building. The lighting produces tremendous heat loads in a structure and obviously from the point of view of audience or artists’ comfort, these loads have to be successfully dealt with. The person concerned with this aspect of the installation will be an air conditioning engineer. One of his main problems will be that to move the vast quantities of hot air requires large amounts of plant and these have to be housed somewhere in or on the building; the other problem being that the air conditioning itself can generate noise. This brings us to another valuable member of the team – the acoustic engineer whose concern will be to ensure good acoustics for either the audience in the theatre or for the reception of sound in film and TV studios. Major concerns to him will be the shape of the building and the noise generated by equipment, such as air conditioning etc. and how this can be adequately dealt with.

Finally, we have two people who will work extremely close together; one of which is the lighting consultant, designing the lighting system and the electrical engineer concerned with the installation. One of his prime functions will be to interpret the needs of the lighting consultant for the wiring, the lighting power sockets and the power supplies needed for the lighting in the building. In addition, he will be concerned with the electrical supply for the air conditioning system and the general lighting in the premises, together with normal power sockets around the building. He will also be concerned with fire detection and emergency lighting systems.

Items to be considered by the project team are as follows:

1 Overall plan

(a) What exactly is the requirement?

(b) Is it a new building or modifications to an existing premises?

(c) Is it a refurbishment?

(d) Is this the final scheme, or is any allowance to be made for future expansion or development?

2 Building construction

(a) Floor

(b) Walls

(c) Ceiling or roof structure

(d) Access to working area

(e) Ancillary and control areas

3 Studio size

(a) Length/depth

(b) Width

(c) Grid height

(d) Overall height

4 Ventilation/air conditioning

(a) Position in studio

(b) Capability

(c) Plant and ducting routes

5 Power system

(a) Method of supply i.e. single or three phase, ‘Star’ or ‘Delta’?

(b) Voltage and current capacity of incoming supply

6 Lighting requirement

(a) Light levels required

(b) Type of suspension

7 Studio requirements

(a) Scenic suspension facilities

(b) Main lighting

(c) Effects lighting (cycloramas, projection systems and automated luminaires)

(d) Special facilities e.g. remote control of lighting power

8 Control and Dimming requirements

(a) Type of lighting control console

(b) Location of lighting console

(c) Number of dimmers

(d) Location of dimmers

(e) Provision of power and switchgear for dimmers

(f) Provision of remote control consoles for scenery and lighting systems

(g) Switching of lighting in remote areas; or, remote control of the system from two or more points

9 Provisions for safety

(a) Smoke detectors/sprinklers

(b) Local authority requirements

(c) Users’ requirements

9.2 Safety requirements

The requirements of safety have a major influence on the installation, and they will ultimately sway the decisions made by the project team.

One of the problems in any premises is fire. It is relatively easy to train the permanent staff manning a building and, for that matter, the artists concerned with the production the safest way to exit from the area of work. It becomes much more difficult with the public, because of the inability to train them in the direction of where to go safely, when a fire breaks out. Thus, there is a need for clearly marked ‘exits’, correctly defined passageways for staff, artists and audience to evacuate a building. Although sprinkler systems are commonly used in the theatre due to the fact they can extinguish fires very effectively, they are somewhat of a hazard in the film and TV industry as generally much more lighting will be involved together with a lot of technical equipment. There is obviously a need, if a fire breaks out, not to damage too much of the existing technical plant. To this end, smoke detectors and ‘rate of temperature rise’ detectors have been used in more recent years to warn the local staff of problems and these can also be coupled through via the telephone network to the local fire department.

With any planned development of any premises, either existing or proposed, it is most important to involve the local fire authority at an early stage so that they are consulted on what should take place within the building. There is a requirement that all the adjacent areas to a studio have to be safe as well, such as dressing rooms, control rooms, dimmer rooms, etc. A good example of applied safety is that of a dimmer room which may have a door opening into the active area itself, will require another access door, generally at the opposite end of the room so that operators can evacuate away from areas of potential hazard. In film and TV studios, there is a need to have defined fire lanes within the studio active area, so that people can exit safely from an area of great potential danger. Most modern studios are built with a marked fire lane, which has to remain clear of any obstructions, around the perimeter. They also have to be equipped with a certain number of exits according to size. In TV and film studios, acoustic barriers are often formed by having twin doors through a small lobby from the corridors adjacent to studios to the studio area itself. It is obviously important that these allow a safe exit.

An area of great concern for safety is the mechanical structure formed above the acting area. This will usually weigh several tonnes and will have pieces of moving machinery sitting on the structure itself. Thus, other than the static load of the weight of the equipment, we have the dynamic loads when the motors and lifting gear are operated, lifting scenery and luminaires from the acting area. Devices rigged to the mechanical structure such as the luminaires, pantographs, technical fittings of any description and scenery equipment all pose areas of potential danger. Almost on a par with the mechanical problems are the electrical problems. Although it is not very likely that an electrical socket will suddenly work free and fall to the studio floor in normal operation, it is possible that any malfunction of the electrical system may cause a fire. It is also important from the operators’ point of view that the electrical system is installed to the highest safety standards.

9.3 Greenfield sites and the refurbishment of existing premises

The architect having been given a brief which may be that of a ‘green field’ site, which means building new premises from scratch, or the refurbishment of existing premises. In the first case, that of new premises, the architect obviously starts with a blank piece of paper and can incorporate many new ideas and suggestions. If, however, it is the refurbishment of existing premises, he is constrained by what he can do within the building, the limits being caused by the physical structure of the building and the loads that would be acceptable to that structure, how much space is there for the development or how can extra space be created within the development. Unfortunately, for the poor architect, every interested technical person has an input which usually conflicts with the rest of the team. For example, it might be that the lighting consultant, to meet the needs of his client, requires to make the area as large as possible, together with extremely high lighting and thus electrical loads, which will cause problems for the air conditioning and electrical engineers. With all these changes to the structure and shape, the poor acoustics specialist starts to tear his hair out with all the extra work that this is going to entail. The structural engineer, at this point, probably has his eyes firmly fixed on the ceiling thinking of all the calculations he has to make so that the architect will be convinced that the building won't fall down.

Having said this, of course, most project teams work extremely harmoniously and usually generate a good team spirit. It is more than obvious at this stage that a great deal of compromise will have to be reached on the installation itself. Thus, where do we start?

In an existing installation, the size of the studio will be fixed, and very seldom will it be changed. It might be that new mechanical devices are incorporated in the new installation or the electrical installation is changed, but generally the size and height of the area is fixed. This is probably a good thing from the architects’ point of view because it places quite logical constraints on what can happen within the area chosen for development. It may be that the existing lighting grid structure remains unchanged, the only alterations being changing the luminaires supplied to the premises. If this is the case, the constraints already laid down by the lifting capacity of the equipment installed will dictate the type of luminaires purchased. If however, some of the facilities are to be changed so that greater lifting capacity can be used, this will have a knock on effect on the structural engineers’ calculations, due to the devices imposing greater loads on the structure. It is quite conceivable that although the weight of the equipment doesn't increase, the power required for the equipment is higher, thus the electrical engineer will have to update his power system and the ventilation engineer will probably have a potential problem with the existing air conditioning plant. The room used to house the dimmers, if such a room exists, which was probably quite adequate, possibly now becomes inadequate by an increase in the number of dimmers required. All of this presupposes that the lighting consultant can actually do what he wants. Unfortunately, in any modern system, we also have to handle scenery. Therefore this places constraints on the disposition of lighting bars in a system, it also dictates the spacing between lighting bars or trackways. The size of the luminaires involved will also dictate spacing in the grid.

A modern controversy that reigns quite a lot these days, is where do we put control rooms? In the theatre, control rooms with a window having a clear view of the stage are obviously desired for those staff operating sound systems and the lighting control console. In television there is not an overwhelming need to see in the studio as the pictures from the cameras will tell the operating staff what is happening. There is however, a need for rapid access for the LD and people concerned with the production from the control rooms to the studio and to this end, many studios built today have control rooms at floor level. A walkover grid is highly desirable for the ease of suspending items of equipment from the grid itself. One of the major problems of walkover grids is the building is required to be higher, or in a fixed building, the proposed grid is forced to be lower. In an existing building, the walls may not be capable of taking additional loads and any new equipment installed would require either building alterations to the walls themselves so that the loads become spread or that structures are used that use the floor area as support. If we are building from scratch on a green field site, most of the problems can be taken care of, hopefully with the ingenuity of the architect and the structural engineer. The main requirement in a green field site would be that of the acting area and its associated facilities. There is always a need for large theatre stages, but common-sense has to prevail and generally the architect, having been briefed by the client as to what the requirements are, has to do his best within the budget to meet the planned objectives.

If we were building from scratch in the film industry, generally we would be building studios with very large acting areas i.e. around 1500 m² to 3000 m². In the film industry, the feeling generally is that a small production can fit into a large studio area but not the other way around. This might appear to be the case for the TV industry as well, but because the studios have defined purposes, such as small news areas, small presentation areas, medium-sized studios or large multi-purpose production studios, there are finite limits to areas required. Most of these are established by custom and practice within the industry itself. Another aspect of film studios is that they are not, generally, permanently equipped with lighting equipment but are usually provided with a fairly basic lighting grid and power supply system.

Television studios are generally integrated into production centres, which may vary from fairly small to very large such as the BBC TV Centre in London. By integrating a series of box like structures into a building, the design of the building is greatly influenced. In TV there is a need for many adjacent areas to a studio such as make-up and wardrobe areas, dimmer room, production, lighting, vision and sound control rooms. The disposition of all these areas has a bearing on access ways and vantage points to the studio. In the theatre there is not the need for so many technical rooms as the production is controlled from the stage area. Most of the support areas have to be close to the stage so that artists are provided with good access to dressing rooms and quick change areas. A requirement of theatre productions is to have complex mechanical stage lifting arrangements, possibly integrated with orchestral facilities. All of these will have to be considered by the architect so as to integrate the whole system to a meaningful production area and the following sections give the various parameters that have to be observed so that the various requirements of the building are met.

9.4 Building construction – how it can be influenced

In film and TV studios, the decisions are somewhat dictated by the needs of the set designer. Generally, in the case of the film industry, ‘big is beautiful’. Large scale studios often have wide vista shots taking place, which dictate the height of any cycloramas used. A studio 32 m long will require cycs at least 9.5 m high and probably higher. If we allow a clearance above the cyc sight line so that luminaires do not intrude, we additionally need at least 1.5 m clearance from the top of the cycs to the grid. If, for instance, boats are used in the studio, then even more clearance is required above the cyc line and this would imply an extra 2.5 m, thus allowing operators to work at this level without hitting their heads on the grid structure. Film studios are not traditionally equipped with walkover grids, but they do require access at high level, even if it's only walkways to allow access for rigging and de-rigging of the block and tackle units to suspend lines for scenery and luminaires. There is obviously also a need to reach the electrical distribution system at this level where luminaires are being used or power feeds have been dropped from the grid down to lights which may be suspended on block and tackle or some other lifting device.

Attempts have been made in the past to provide some form of mechanised system similar to those used in the TV industry. The most famous of these was the installation of a monopole system in two studios at Pinewood in England. For most of the time however, the film industry is content to go on in the same way that it's practised lighting for many years. Thus the prime requirements of the film studio are suspensions trackways at fairly frequent intervals down a studio so that lifting equipment or ‘boats’ may be attached where and when desired. Due to the sheer physical size and subsequent weight of the luminaires used in the film industry over many years, the grid structures have had to be reasonably robust to take the weights of the equipment. However, it should be borne in mind that saturated lighting with its well distributed weight load, is not used in the film industry. One of their main requirements is high point loadings caused by several large high intensity luminaires, or a ‘boat’ with luminaires attached, in one small area of the grid structure.

With the construction of a new film studio, it might be that we would have to integrate its use for either film or video shooting. Much of the economy of the film industry these days is based upon the shooting of pop videos and commercials for TV. Film studios are fairly simple in their nature being rather large ‘box-like’ structures immune to outside noise if designed as sound stages, and constructed in such a way that almost any production can be fitted in them with the provision of high cycloramas. The actual lighting arrangements are extremely basic. The film industry occasionally use dimmer units for some control on productions. The one big advance that has helped in the film studio is the introduction of discharge lighting taking away the need for the large carbon arcs. These units, with their highly efficient output require much less power from the electrical system. Talking about power in systems reminds us that some film stages may still have d.c. voltage feeders, although in most cases these are being converted to a.c. systems. Generally there is no need to provide permanent dimmer rooms adjacent to film studios, although if new studios did evolve for dual purpose film/vision systems, then a provision should be made so that fairly large dimmer installations could be added at a later date in the studios’ life. The general requirement in film studios is for large power distribution cabinets, placed at regular intervals around the studio from which can be taken all the temporary feeds to the lighting units themselves. Whereas in TV studios highly sophisticated air conditioning systems are used, the film industry is still fairly basic in its requirements. Due to the nature of filming, which may be a rehearsal period and then a ‘take’ with long extended intervals between, it is easy to allow the premises to cool over periods of time. Although it must be said, that in modern TV studios the use of rehearse/record techniques using a few sets at a time diminishes the requirement for the large air conditioning systems at present employed.

Due to the need to contain costs within the TV industry, it is strongly suspected that other than refurbishing existing studios, very few new studios will now be constructed, in either Europe or America. What may be required is the conversion of some premises for studio use.

Let us now turn our attention to the design of lighting systems for TV studios and how those designs will influence the building construction. Large TV studios generally use a complex grid which in itself poses installation problems but prior to that is the need to ascertain the height of the grid and clearance above for services and personnel. There have been cases over the years where the management and accountants were convinced by the arguments put forward by architects saying that for each 300 mm of additional height in a studio enormous additional costs were incurred. Thus certain studios were limited in height, only to find the programme makers were forever complaining about the limitations imposed in these studios. As a starting point it is extremely important to get the height of the studio correct and the following system gives the method of calculation. It is relatively easy to decide upon the acting area that is required and consequently the floor dimensions. However, an important parameter that can only be ascertained by examination of the camera viewing angles is that of the cyc height and its subsequent effect on wide shots in a studio.

In small studios, more than likely, the cyclorama track and hence the cloth hanging from it will be relatively close to some of the walls, the only space required behind is for the odd low level lighting outlet box with space to plug in sources without impeding on the cyc cloth itself. In larger studios it is normal to have a walkway behind the cycs where space is not so critical from the point of view of the cable outlet boxes. When designing lighting for a cyclorama, the question is often asked, is top or bottom cyc lighting the best? The answer is – neither – it depends what type of result is required. One of the main essentials is to have good coving arrangements at the base of the cyc to get a blend between the horizontal and vertical so that there appears to be one continuous surface from the camera's viewpoint. Top cyc lighting, which is plotted at 3.1 m away from the cyc at 2.5 m intervals, will give very good results from a height of 10 m down to floor level. However, bearing in mind that the light is striking the cyc cloth at a very acute angle, and striking the floor almost straight on, gives differentials between the base of the cyc and the floor which are very difficult to overcome. The great advantage of top cyc lighting is no floor space is required, and indeed, in small news and current affairs studios, almost essential to prevent problems with space in the studio.

Bottom cyc lighting, which is generally used 1 m away from the base of the cyc, with each individual source of light at 1.2 m intervals, can give a very even horizontal wash on the cyc but gives a very bright horizon effect at the base of the cyc and fades off rather rapidly in the vertical. If the units are taken out into the studio by the same amount as top units, i.e. about 3m then we could generally expect a much more even result but as is obvious, this is not practical and it may be that the bright horizon effect is quite desirable. However, it is essential with groundrow units that they are hidden in some way unless the units themselves are not too unattractive to appear in shot. Two methods of hiding groundrow units are used; one of which is to have a short cove around the studio on the inside surface between the cyc units and the acting area, or to place the groundrow units in a well which runs parallel to the base of the cyc, which can be very effective in long shot, but unfortunately when cameras are used off centre, can pose a problem inasmuch that the well itself may become noticeable.

With a camera viewing aspect ratio of 4:3, if a 36° lens angle is used this gives a vertical angle of 27° (Figure 9.1). When using a 16:9 aspect ratio system the relative cyclorama heights remain the same but the horizontal angle will have increased.

Note: By knowing the aspect ratio and horizontal angle of view, the vertical angle can always be derived.

Assume a lens height of 1.8 m above floor level. Cyclorama height = (L × tan 13.5°) + 1.8 m (where L is the length of the studio). Cyclorama heights (in metres) for studios with maximum length (in metres) are shown in Table 9.1.

Figure 9.1 Camera angles

Table 9.1

Studio length (m)	Cyclorama height (m)	Studio length (m)	Cyclorama height (m)
6	3.2	20	6.6
8	3.7	22	7.1
10	4.2	24	7.6
12	4.7	26	8.0
14	5.2	28	8.5
16	5.6	30	9.0
18	6.1	32	9.5

As an example to see how the studio height has been influenced by the choice of the cyclorama height the following example is given.

Studio dimensions	= 30 m × 24m
Cyclorama height for 30m	= 9m
Height allowance above the top of the cyc for luminaires and pantographs from thesuspension system	=2m
Therefore the grid height	=11m
Allowance above the grid for maintenance	= 2.5m
Allowance for air conditioning and services above the grid maintenance area	= 2.5m
Total studio height	= 11 + 2.5 + 2.5 = 16m

The example quoted is for a conventional studio with a barrel grid. The figures still hold for monopole grids, but if no access is required above the grid, or ventilation is provided such that access is not impeded, then the total height could be reduced. In the smaller studios little or no access is required at high level, the only space requirements generally are for the air conditioning equipment and electrical services.

9.5 Structural loads

Monopole installations

Monopole grids consist of continuous longitudinal trackways at very regular intervals usually engineered from steel, because they will wear so much better than lighter weight materials such as aluminium. At right angles to the main trackways, again at regular intervals, are the changeover tracks to enable monopoles to be wheeled from one track to another.

The method of construction of a monopole grid is to have a series of oblong platforms, made from steel with aluminium decking infill, individually suspended from the under side of the primary steels which will generally be used to support the roof of the studio. The long sides of the platforms form the main trackways and the short sides are the cross over tracks. The slots provided in the grid for the monopoles are conventionally 63.5 mm (2.5 inches) wide.

In the monopole system the mechanical loads on the structure can move around the grid; in comparison, a barrel grid, because of the design of the system, spreads the structural load fairly evenly. If we take as an example a monopole capable of lifting 60 kg, it will have a self weight of approximately the same amount, thus its total overall weight will be 120 kg. Therefore the point loading on the grid is 120 kg every time one of these units is used. The next problem arises when considering how many units per linear run could we use and for TV it is quite possible that a high density of monopoles have to be provided and allowance has to be made for the units to work almost next to each other, although it is doubtful that more than about 20 would be used in any one cluster. For the structural engineer concerned, the problem is that these large lumps of metal can move around the structure and can appear almost anywhere. Therefore a monopole grid has to be extremely strong and thus tends to be quite heavy. All this creates loading problems for the structural engineer and the architect to incorporate in their design. To give some idea of possible loadings in a studio it may be that 120 motorised monopoles are used in a studio of some 600 m². This represents a load, just for positioning the lights, of 14.4 tonnes. If there is a need to cluster the light sources; as an example, 16 lights formed into a square would occupy approximately 4 x 4 m and present a load of 1.92 tonnes to that area, which of course is a high point loading.

Another problem arises inasmuch that if we started all the units up at the same time, the dynamic load on that portion of the grid would be quite considerable and we certainly don't want it springing and oscillating every time we move equipment. Therefore, it has to be reasonably rigid, and this requirement also dictates the needs for fairly massive grid structures. In addition to the basic grid, there will be a need for loading platforms adjacent to the grid for rigging monopoles into the trackways. Possibly suspended just below grid level around the studio, are walkways, used for access to power feeds and specially rigged peripheral luminaires. Approximately 1 m from the edge of the studio a permanent cyc track will be provided. Trap doors have to be provided for lifting equipment into the grid area: either built into the grid itself or provided at the side of the studio. Due to the highly flexible nature of monopole grids they only require a certain basic amount of luminaires because these can be moved around to suit the production. Figures for luminaire requirements are given in the next section.

Barrel installations

Many American studios are equipped with counterweight barrel systems where the length of the bar may be around 4–5 m long. Studios are generally equipped with a reasonable density of this type of barrel. The nice thing about counterweight bars from the structural man's point of view is that the load on the grid is usually the basic SWL of the bar itself and most of the weight is contained within the counterweight system, usually mounted on the studio walls. Some barrel studios have been constructed with bar units in the studio area with the support wires taken via diverter pulleys to the edge of the studio where the motor units are mounted on the walls. In most modern barrel studios where the scenery handling facilities are integrated into the grid structure the motor winding units for the scenery lifting system are generally mounted on the side walls of the studio. Most of the problems for the structural engineer with grid designs, usually arise with the heavy motorised barrel units which may be of the standard type with motors mounted at grid level or self climbing units with integral motors. Even if the system uses self climbing units, the total weight presented to the grid structure at any point is approximately the same.

Most barrel studios are usually constructed with the bar units approximately 1.5 m apart with an end to end spacing of approximately 1 m. Thus having been given the studio area which doesn't include the fire lane, it is relatively easy to work out how many bar units will be employed. To take account of cyclorama tracks which have a radius at the corners of the studio, short bar units may be employed in the four corners of the studio.

In a monopole grid, because the slots provided at grid level are very similar to those in the theatre, it is relatively easy to drop spot lines for holding scenery up or suspending scenery pieces. In barrel studios, it is important that provision is made for the use of scenery and many modern studios have specially installed scenery winching systems, which run in between the main bars themselves. It is fairly obvious that the easiest installation for scene winches is in the same orientation as the bars. Going crosswise across the bar system could pose considerable problems. Motorised barrel winch units when they are of the standard type, are usually supported lengthways along twin structural members.

In a studio of some considerable span, these members have to be supported at frequent intervals to take account of the load. Thus several upright members between the grid and the primary steels have to be used so consequently it is not totally unobstructed. This point has to be borne in mind when designing walkover grids so that access is reasonable. A typical barrel winch unit will weigh approximately 150 kg, with a lifting capacity of almost the same amount, so the total load on the grid from any one winch unit may be around 300 kg. The encouraging thing from the point of view of the structural engineer and architect is the fact these loads are fixed in position in the grid. The weights given here assume the use of bar units approximately 2.5 to 3.0 m long. If we use shorter units the relative weights are somewhat similar from the point of view of the structural man, i.e. a shorter bar unit may have only half the lifting capacity of a long unit and its motor unit, mounted at the grid, may be only around 75% of a big unit but we will use twice as many bars in the studio. Thus the total load on the grid is approximately the same.

Most studios fitted with barrel systems operate with a high density of lighting. It may be at the BBC where multi-purpose luminaires are rigged permanently to the barrels, or like some of the studios in America where many 2 kW and 1 kW luminaires are rigged per barrel, just for the ease of the general operation.

It is more than likely, in many of the studios that use motorised devices, for some restriction to be placed on the amount of units used at any one time, to stop dynamic loading problems on the grid.

Smaller studios such as those using motorised or spring pantographs will have long trackways where rather like the monopole studio the loads can be grouped in areas. The weight of equipment in these studios is significantly less than motorised barrel and monopole systems. However, due to the nature of operations in studios of this type, their load is fairly well spread throughout the structure and of course, can be contained by loading notices which prohibit too much clustering within the studio area.

Perhaps only about 40 luminaires may be used together with 40 suspension points and of course this does not present the problems that exist in a large studio. Small roller barrel grids can also present a moving load to the main structure, although by not using motorised units, the weight on the structure is considerably less. In the larger studios such as those used with monopoles and motorised barrels which may have their motor units mounted at grid level, or be the self climbing type, special metal structures have to be arranged usually by the structural engineer in consultation with the architect, so that the rather heavy lighting grid system can be installed safely. This may require the use of special large beams being incorporated into the structure at high level. It must also be remembered that other than a lighting grid, air conditioning requirements exist and there will be a lot of additional weight from the power wiring system etc. In smaller studios it may be that grid attachments can be made to, for example, a concrete roof going over the studio which can be made sufficiently strong by the astute use of reinforcing rod. The saving grace in a smaller studio is that the spans are not so great.

Figure 9.2 Typical studio layouts: (a) fixed barrel grid; (b) roller barrel (c) motorised barrels

So far we have discussed the installation of grid systems and their subsequent structural loading, on the assumption that we are in a new building and can influence the design. What happens if we require to put a lighting system in existing premises? First of all it is important to come up with the lighting scheme itself, which can then be presented with all its facts and figures to the architect and structural engineer concerned. They will obviously be able either to accept the scheme as it stands for the new design, or it may be that they are able to modify the building in some way to accept the new design. Therefore it's back to the poor old lighting consultant to come up with an idea to be contained within the parameters set by the architect and structural engineer. It's quite possible that the idea could be acceptable but with some change to the structure itself, such as spreading the loadings between the walls and the roof, not just using the roof itself. It may be that the roof structure cannot accept any load other than the one existing, therefore all the new installation would have to be supported from the side walls or from a structure built up from the floor level. The first of these requires that the walls are strong enough, and the second that the floor is also strong enough. Any of these solutions may be acceptable and it might even be a combination of any of them or all three. It must be remembered when discussing the structural arrangements with the architect and structural engineer, that these figures have to include for all the lights, all the rigging system, all the power system and any ancillaries that may be added at any time.

In addition to the structural loads presented by the lighting system in the studio, the structural engineer will also be concerned with the size of plant installed in areas adjacent to the studio. Generally, the weight of the switchgear will be spread out in a fairly uniform fashion. The input power cables to the switchgear and the cables from the switchgear to the dimmer racks will also be fairly well distributed throughout the area. Most of the problem will be concerned with the weight of the dimmer racks where in a large installation the structural engineer may be confronted with a room with up to 20 or 30 dimmer racks. Dimensions of dimmer racks vary quite considerably, and as an example, a lightweight rack of 200 kg from one manufacturer has base dimensions of 905 x 510 mm whereas another, which is a high density rack weighing 900 kg with base dimensions of 850 x 600 mm. The latter rack obviously gives floor loading problems, being a large weight over a small area. It would seem at first sight that the best solution to any of the loading problems in dimmer rooms is to keep the weights of the racks low and use more racks so that the loadings are well spread. However the size of the room dictates how many racks may be used and the economics of the situation is that more racks generally put up the cost. In a new building, the structural engineer would obviously cater for the high floor loading at the planning stage; in existing buildings however, special precautions will have to be taken, or it may be that additional building work is required.

In practice, over many years of experience, it is very seldom that we have found buildings to be so bad that they would preclude some form of solution being adopted albeit possibly far removed from the original concept.

9.6 Television studio requirements

The influence on the structure caused by the lighting grid has nothing to do with the amount of luminaires to be provided. Grids are there to hang lights, almost anywhere, using whatever quantities of luminaires that may be available. The basic requirement in any TV studio is for a certain amount of light to satisfy the technical requirements of the cameras. This quantity of light will be determined by the average reflectivity of scenery together with the exposure time of the camera coupled with the aperture of the lens in use. Based upon incandescent sources with an efficacy of around 26 lumens/W we can measure the amount of power required for the acting area to be adequately lit and this is given in Watts per square metre. At the present time, a figure of around 300 W of lighting/m² for the basic lighting is considered adequate for the majority of general purpose requirements in TV. Many TV studios today will use prompters mounted on the cameras; these reduce the reflected light to a camera by about half a stop and the incident light level has to be raised by 33% to compensate.

For example:

• Normal light level required: 600 lux.
• Prompter loss of 1/2 stop effectively reduces light level to 450 lux (75% transmission).
• Light level to achieve 600 lux = 600/0.75 = 800 lux, which represents an increase of 33%.
• Now the prompter loss of 1/2 stop reduces light level from 800 lux to 600 lux, the level initially required.

This is usually accomplished by utilising higher powered light sources or raising the dimmer output levels. It may be that the dimmer settings are quite high e.g. ‘8’, ‘9’, and it is impossible to achieve the correct incident light level. This may necessitate, for example, having to choose 2kW instead of 1 kW luminaires. In larger luminaires, this can be overcome by using higher powered twin filament lamps or moving from 2 kW to 3kW lamps.

Although the figure of 300 W/m² is satisfactory for most basic purposes, it should be borne in mind that additional requirements, such as cyc and effects lighting, will impose an additional burden. A colour mixing system used on cycloramas will probably require loads of anything up to 2000 W/m of linear run, thus a 40 m cyclorama cloth might require anything up to 80 kW being provided for adequate effects purposes. Although the cyc lighting power figure seems over generous it must be noted that when using highly saturated filter colours with transmissions as low as 5% the light output needs to be high to create the maximum effect and it is therefore suggested that a slightly higher estimating figure of around 450W/m² is used on any studio above about 250m². An important fact in the choice of luminaires is the size of the studio. Studios up to about 150 m² will generally work quite happily with a 1 kW fresnel as the highest power luminaire required. However, above this size of studio, the majority of luminaires will probably settle at 2 kW, 3 kW or 1.25/2.5/5 kW. These powers of course, are related to working distances involved between the lights and the various subjects.

Whatever estimating figure we use for the power requirements for a studio, be it 300 W/m², or 450 W/m², it is obviously relatively easy to work out the power requirement by taking the active area in square metres and multiplying it by the appropriate wattage figure. In the case of monopole studios, and the smaller pantograph type studios it is more than likely that the power requirements of the supply system will more or less match the available total wattage of the luminaires used. However, in the case of saturated lighting grids, the total power of the luminaires installed will probably exceed the power available by a factor of anything up to three times. As an example of this, a BBC studio of 800 m² will be supplied with approximately 450 kW of power. The 100 bars installed will each have two 3.75 kW luminaires rigged on them, thus the load presented by the luminaires to the system is 750 kW. In practice this is not a problem as only selected numbers of lights are used and therefore it is a basic requirement that the LD must have current meters and/or an alarm system indicating the maximum electrical load. The figures that follow have been worked out from typical studio usage over many years and represent reasonable requirements of any studio. It is obviously easy to start equipping a studio by covering the basic lighting requirements and in the fullness of time purchase more equipment to suit the installation. As an approximate guide, the ‘luminaire power’ required is divided into 2/3 hard sources and 1/3 soft sources.

9.7 The smaller studio

The smaller studio (those from 20 m² to 80 m²) usually provides for ‘fixed head’ presentations.

They are quite often conversions of existing premises with little or no air conditioning. The floors are usually strong, but the walls or ceiling may require some modification to allow a simple grid to be installed and this is generally because of the imposed weight of the grid and luminaires. If the main grid can be suspended from the ceiling all that is needed at the sides of the studio are cyc rail supports. Or it may be that the cyc system is integrated into the main grid structure. On occasions, however, the ceiling will be not strong enough to support the weight of the grid and it will be necessary to either fix to the walls or have a floor standing structure to support the grid. Quite often height is a problem and deep primary support beams, for the grid, across the studio will make matters worse. The use of a light weight truss can be advantageous if a floor standing structure has to be installed.

50 m2	100m2
Minimum power required: 16 kW	Minimum power required: 30 kW
12 × 1 kW Fresnel spots	18 × 1 kW Fresnel spots
6 × 650W Fresnel spots	8 × 650 W Fresnel spots
8 × 625W tungsten softlights	10 × 1.25kW tungsten softlights
or	or
8 × 220 W Fluorescent softlights	10 × 220 W Fluorescent softlights
4 × 575 W Profile spots	6 × 575 W Profile spots
4 × Floor stands	6 × Floor stands
Cyc:	Cyc:
12 × 625W single compartment	16 × 625 W single compartment top
top units (1.2 m from cyc)	units (1.2 m from cyc)
150m2	250 m2
Minimum power required: 50 kW	Minimum power required: 75 kW
24 × 1 kW Fresnel spots	10 × 2 kW Fresnel spots
10 × 650 W Fresnel spots	30 × 1 kW Fresnel spots
10 × 1.25kW tungsten softlights	16 × 1.25kW tungsten softlights
or	or
10 × 330 W Fluorescent softlights	16 × 330 W Fluorescent softlights
6 × 575W/1 kW Profile spots	6 × 575 W/1 kW Profile spots
8 × Floor stands	10 × Floor stands
Cyc:	Cyc:
30 × 625W single top units	20 × 1.25kW twin top units
(1.2m from cyc)	(3m from cyc)
and/or	and/or
30 × 625 W 4-compartment	40 × 625 W 4-compartment
groundrow units	groundrow units
400 m2	750 m2
Minimum power required: 180 kW	Minimum power required: 320 kW
3 × 10 kW Fresnel spots	6 × 10 kW Fresnel spots
6 × 5 kW Fresnel spots	10 × 5 kW Fresnel spots
20 × 2kW Fresnel spots	35 × 2kW Fresnel spots
40 × 1 kW Fresnel spots	70 × 1 kW Fresnel spots
or	or
48 × 1.25/2.5 kW Fresnel spots	85 × 1.25/2.5 kW Fresnel spots
and	and
12 × 650 W Fresnel spots	20 × 650 W Fresnel spots
24 × 1.25kW tungsten softlights	40 × 1.25kW tungsten softlights
or	or
24 × 330 W Fluorescent softlights	40 × 330 W Fluorescent softlights
8 × 575W/1 kW Profile spots	12 × 575 W/1 kW Profile spots
20 × 500 W Par-cans	40 × 500 W Par-cans
12 Floor stands	16 Floor stands
Cyc:	Cyc:
16 × 1.25 kW 4-compartment	30 × 1. 25 kW 4-compartment
top units (3 m from cyc)	top units (3m from cyc)
and/or	and/or
40 × 625 W 4-compartment	70 × 625 W 4-compartment
groundrow units	groundrow units

The most basic grid is a fixed matrix of steel barrels, although if weight is a problem aluminium can be used at a cost premium. The matrix should provide a spacing no greater than 1 m and preferably 600 mm. However, the less the spacing the more the weight load and cost! A good alternative is to use roller barrels which allows for better positioning of luminaires and can cut down the amount of metal in the grid structure. Usually a twin cyc rail is quite sufficient and the cyc cloths will usually be lit from above to conserve the limited floor space. There will be a need for Chromakey backings which can be provided by a cloth or by a fluorescent back lit panel. Access behind the cyc cloth will be fairly restricted, but there will be a need for some power sockets at studio floor level for floor-stand mounted luminaires and effects lights. The choice of lighting can be made from tungsten for the best control of optical performance and lighting level which is controlled by a dimmer. Unfortunately this can cause problems with heat therefore a hybrid solution can be adopted by using a mixture of tungsten hard lighting with fluorescent softlights. The dimmers will be controlled by a very basic lighting console. The amount of facilities will depend upon the complexity of programmes, which in a small studio are very limited. The main requirement of the lighting console will be very rapid access to any channel as it is more than likely that rehearsals will be very brief affairs.

9.8 Air conditioning requirements

If we install 100 kW of tungsten lighting in any area, we have to expect that, ultimately, all of this will appear as waste heat and most of this will rise vertically. From the point of view of air conditioning, two effects take place. The first is that the luminaires will radiate infrared energy in the direction of the artists. This radiation is in direct proportion to the efficiency of the luminaires themselves, thus a luminaire with a claimed efficiency of 26% will have approximately 26% radiant energy in the light beam; the remainder will be contained within the luminaire and subsequently re-radiated from the luminaire body or as exhaust from the ventilation system on the luminaire itself. Generally older premises are never provided with adequate air conditioning systems and it always seems ‘that you have to sweat to earn your money’! However, in new premises or where premises are capable of being successfully converted, it is possible to have adequate air conditioning installed. Thus, there are two important areas from the point of view of the air conditioning man: first of all, the conditions that create a comfortable atmosphere at the acting level and secondly, the conditions for people working either in the flies or at grid level itself, and it is at grid level where the maximum heat will eventually settle, assuming nothing is done to prevent it.

Heat loads are rather like the domestic electrical load and are somewhat subject to diversity of use. It is very seldom that all the installed lighting in any system will be used at the same time, and over a period of some years it has been established in TV, that an average load of 66% of the maximum installed kilowatts will be used over a period of time. So, for a studio using 400 kW of lighting power, we need to worry about 264 kW worth, thus easing the burden on the air conditioning man. In film studios, although large amounts of power are used on film sets, they are usually used for reasonably short periods of time with breaks between, which allows the temperature, although perhaps having reached high levels, to be dissipated fairly quickly by the use of large fans in the roof or walls. Television has changed greatly in recent years and the technique of rehearse/shoot, generally means that only perhaps one or two sets of the possible 10/13 sets in a large studio are in use at any one time, thus the load on the air conditioning system is considerably less and it may be in the future that the estimating figure of 66% needs to be looked at once again and possibly reduced.

It's all very well having air conditioning that works effectively and keeps the ambient temperature to reasonable limits, to the relief of everybody concerned; however air conditioning can only be achieved by moving a large volume of air down small ducting or an equal volume of air down a large ducting system. The latter will create, in general, much less noise, and in fact for TV use, we have to be extremely careful with the generation of noise from the air conditioning system. An interesting coincidence occurs inasmuch that by moving large volumes of air we don't create some of the air movement that causes problems in practice, such as a cyc cloth being moved by the sheer volume of air flowing around a studio. Other than the needs of the studio, air conditioning will be required in the dimmer room, as there is a reasonable amount of waste heat generated.

This is particularly important if the dimmer room doubles as a maintenance room for the electricians to use. In a large studio it may be that the air conditioning engineer concerned will be able to have a zonal control system so that when only one quarter of the studio is used only that quarter is air conditioned to any reasonable degree. The requirement for a large volume of air to be moved down large ducting, obviously implies a large space being occupied by the air conditioning system at grid level. Thus, it is extremely important when planning a studio, to integrate the air conditioning system and the lighting grid system together, so that a clash of interest does not occur and certainly access to the lighting equipment is not prevented. Others affected by the requirements of air conditioning are sound, vision and electrical technicians who also require the use of certain portions of the grid for some of their systems. Some air conditioning systems, when moving the volumes of air suggested in this section, require large rooms in which to put plant, and these rooms can almost approach the size of some of the studios they service. Further problems associated with air conditioning are that chilled water is required and if compressor units are used, it is important they do not create any undue noise in the studio. It also happens that introduction of air conditioning breaches the walls around the area which consequently cause problems to the acoustic specialist; this latter problem will be discussed in Section 9.10.

9.9 Power requirements

We are sometimes asked about the problems of interference with the use of discharge lighting in a studio as opposed to tungsten lighting with dimmers. Solid state flicker free discharge ballasts, although capable of generating high levels of interference are usually engineered in such a way that interference is minimised. At the present time the EMC regulations would ensure that all solid state ballasts conform to a low degree of interference capability in the same way that dimmers have to be treated.

Irrespective of whether we use 1 kW, 2 kW, 3 kW, 5 kW or 10 kW luminaires, or whatever type of dimmers drive them, power has to flow from one area to another, and this involves large numbers of cables which have to be routed from one area to another with absolute safety. The system that supplies the power has to be carefully worked out and this is conditioned by whether or not it is a new installation or the refurbishment of an old installation. Various parameters concern us when we move power from one location to another and most important of these would be cable size. What affects the cable size? All cables have a small resistance and the larger the cable the less they impede the flow of current. Therefore if we use cables which are high in resistance to the flow of current we will waste some power in the cables themselves and this can cause problems from two points of view; one of which is that the cables heat, which is dangerous or secondly, we lose valuable power in the cables and do not deliver it to the lamps, thus we get a volts drop and the lamps do not work at their maximum efficiency. How do we get around this problem?

The best method is to use generous sized cables and keep the distance from the dimmers to the luminaires as short as possible, bearing in mind possible acoustic noise problems. In film and TV the luminaires tend to be used with reasonably short flexible leads attached so that most of the volts drop is in the fixed wiring. The heating of the fixed and flexible cables by not being large enough in current carrying capacity is, however, very serious. With new installations the present legislation in the UK prevents cables being used which are quite simply not up to the job. However, in old installations, it is more than likely, if refurbished, they will have to have a completely new electrical system.

It is preferable that all dimmers are grouped together in a purpose built room where the noise can be contained and ventilation controlled fairly easily. Circuits should be run as phase/neutral pairs usually with a common earth provided either by large cables to groups of sockets or by the trunking used to distribute the power system. Unswitched sockets should be used and at the present time in the United Kingdom plugs and sockets to BS 4343 are used in 16 A, 32 A and 63 A ratings, and these should be installed as a matter of course in a new installation and wherever possible used as replacements in existing installations. Parallel sockets are provided for convenience on the radial circuits used with the responsibility for the electrical loading of the system being placed on the operators.

Most dimmers in use today are the thyristor type, and we have already discussed the interference that these units can generate. In addition to the thyristor dimming circuits, independent or ‘non-dimmable’ circuits are also required. These are used for electrical loads such as the motors on effects lighting units, fan units and discharge lights including follow spots. It is relatively easy to provide such circuits from contactor switched power although most dimmer manufacturers offer ‘non-dim’ circuits through their dimmer racks, by either bypassing the action of the thyristors or having thyristor dimmers that, in full conduction, stay relatively stable when this type of load is applied. Other than the permanently supplied lighting power for the units contained within the premises, there is a need for additional power supplies when temporary lighting and sound equipment is provided by touring companies. From the point of view of cost, it is important that the dimmer room is as near as possible to the socket outlets used for the lighting system, thus cutting down the amount of cables required between the dimmers and the lights themselves.

The requirements of the film studio for luminaires and dimmers are less demanding than those for a TV studio and the majority of cables used will be flexible feeders and not part of the fixed installation. The biggest difference will be the provision of much larger power supplies. Whereas, for years, the film industry generated their own d.c. voltage, they now rely on the incoming a.c. mains supply.

For TV, in general, we are looking at light levels between 300 and 800 lux, with 60% from keylights; 40% from the fill to give a reasonable contrast ratio. Although in recent years there has reduction in incident light levels this does not reduce the number of luminaires required, only the size and power. In studios which are equipped with dual source luminaires, there is no effect on the luminaires, the only requirement is that lower powered lamps are fitted.

With a more energy conscious society and owing to the need of lower power in installations and heat loads, it is worthwhile considering fluorescent lighting, although this gives reasonable light levels, it is not as good for modelling as Fresnel spots. New installations are, quite often, a mixture of tungsten keylights and fluorescent softlights.

It is possible to use discharge lighting such as the MSR, HMI, etc., to give high light levels and less heat in an installation. One problem with using discharge sources is that they are only capable of being dimmed from a maximum down to 50% light output, and this somewhat limits the control available to the lighting designer, although they may be designated ‘hot restrike’ lamps, they only come on at full power if they have been off for a short period of time. When struck from cold, they still require a warm-up period to achieve maximum light output, which may be a minute or more. It is possible, of course, to fit some type of mechanical dimming to discharge sources and the drawback to this is the noise that may be generated. It is not possible to do lighting changes as such due to the fact that we can never go below 50% light output on the dimming curve. Therefore, discharge lighting is only suitable for studios where the lighting set-up is fixed, i.e. no lighting changes take place. To integrate discharge and tungsten lighting requires one or other being filtered to the correct colour temperature. Another problem that exists in this type of installation, is that all the devices require ballasts and a choice has to be made between standard and flicker free, and it is only the flicker free that allow the 50% dimming to take place; therefore the costs are much higher than would be with standard ballast units. Furthermore, when using flicker free ballasts, some care has to be taken in the installation so that the levels of electromagnetic interference are kept to a minimum. Generally the housekeeping concerned should be the same as when using dimmer systems, i.e. that the wiring feeding the fluorescents, etc. should be kept reasonably well separated from all the sound and vision circuits.

9.10 Acoustic requirements

It's no good having a wonderful building where we are unable to hear the artists perform or for that matter resolve the sound spectrum fairly accurately within a broadcast studio.

What has lighting got that influences the acoustics to any degree? In the film and TV studio there is a requirement to ensure that noise does not come from any of the electrical plant into the studio area. In film studios, generally, this shouldn't cause too much of a problem as dimmers are not the norm in this situation. They will probably have more problems with the use of discharge light sources on the sets themselves and the ballast units used with them. In TV however, there is a problem with the use of many dimmers which are usually positioned very close to the studio, and one of the problems we have is that we make holes in the walls by taking the trunking from one area through to the studio and hence allow some form of vibration to go through the structures. Even if we inhibit vibration by using rubber mounts, or even discontinuous pieces of trunking, it may be that the noise comes from around the hole made in the studio wall and this does cause a real problem in studios. It's very convenient to have a door from the studio through to the dimmer room, but in most cases these have to be carefully selected acoustic doors, and usually double ones, to prevent noise coming from the dimmer room to the studio. Studios are usually formed as rather large box like structures with a metal grid, some 3m below the actual roof. Television studios are generally designed to have a fairly ‘dead’ sound and any reverberation required is added artificially, thus the acoustic specialist has to provide some form of acoustic boxes on the ceilings above the grid where space is at a premium. There is little or nothing he can do below the grid owing to the nature of productions and the usage of the system. The acoustic specialist will also want to cover the walls in acoustic cladding of some description, but unfortunately is bedevilled by lots of trunking and large control consoles at fairly regular intervals around the walls of the studios. This would either be for the lighting system or the sound and vision system. However good the acoustic specialist is, matters are not always controlled by his skills. The biggest problem in studios can be the noise generated by the lights. If the choice of luminaires leads to creaking bodywork on heating up and cooling down of a luminaire, this is absolutely disastrous. Lamp sing can penetrate the quietest of conversations. So whether we like it or not, the lighting systems have a major impact on the acoustics and sound quality of any building used for entertainment.