Lighting Designs for AV Spaces

Introduction

The presentation of text-based content, images and video is an essential part of modern teaching spaces and the clarity of this content is critical to the successful use of modern teaching and meeting venues. Poor lighting design can ruin the effectiveness of presentations making them washed out and difficult to read, as well as failing to provide enough illumination to presenters, whether in a physical space for the local audience, a recorded session or live stream/web conference. Consequently, the importance of lighting design in all presentation, teaching and meeting spaces cannot be over-emphasized.

Design Goals

The lighting design in a presentation space aims to achieve the following outcomes:

  • Control all artificial and ambient light to afford the viewer:

    • appropriate contrast ratio in projected images for their requirements;

    • a clear view of displays, unobstructed by glare and reflection.

  • Provide the required note-taking and task lighting for students.

  • Properly illuminate the presenter in the presentation area(s).

  • Properly illuminate any demonstration and presenter work areas, including writing surfaces.

  • Provide the proper spectrum of light for the appropriate colour rendering of an object.

  • Provide simple, intuitive controls to the user.

  • Use automation to optimise system performance, conserve energy and extend the useful life of fittings.

Relevant Stakeholders

The stakeholders involved in the lighting design of any construction project and their areas of interest are typically:

End users

  • The audience and the presenters are the primary reason for providing an appropriately illuminated environment.

Facilities management and capital projects teams

  • Require finished spaces which are fit-for-purpose.

  • Must meet the appropriate local institution, national and international standards.

  • Need to fit within each organisation’s targets for capital and maintenance costs.

Architect, Electrical and lighting designers

  • All members of the design team require a clear brief.

  • Architects are responsible for the functional and aesthetic look and feel of the space.

  • Lighting designers are generally the experts tasked with achieving performance criteria.

  • Electrical engineers provide feedback to the design team and document the electrical systems required to support the lighting design, ensuring they are functional.

Organisational AV technical and project managers

  • Should be prominent in helping to brief specific lighting performance requirements of each space type, based on local institutional, national and international standards.

  • Need to budget appropriately for the design and installation of projection and display systems which are supported by the lighting design.

  • Should be involved in integration with lighting control systems so as to optimise the user experience of a space.

Standards Compliance

Building code compliance requires that lighting must meet Australian and New Zealand Standards AS/NZS 1680 for Lighting (as amended) and the relevant government building codes. Specifically, lighting must conform to the relevant sections of:

AS/NZS 1680.2.1:2008 (as amended)

Interior and workplace lighting - Specific applications - Circulation spaces and other general areas

AS/NZS 1680.2.2:2008 (as amended)

Interior and workplace lighting - Specific applications - Office and screen-based tasks

AS/NZS 1680.2.3:2008 (as amended)

Interior and workplace lighting - Specific applications - Educational and training facilities

Note that it is common for individual organisations to have their own specifications in conjunction with these standards and advice should be sought from relevant personnel.

Lighting-Specific Definitions

Please see glossary for general definitions used throughout the AETM guidelines.

ANSI Lumens is the projector light output as per the ANSI measurement standard.

Lux is the unit of measure of the light falling on a given area (illuminance).

Maintained lux is a calculation of the illuminance achievable after a maintenance or de-rating factor is applied to the lighting fixtures through the design process, often 0.8.

Luminous flux is the amount of visible light emitted from a light source. Measured in the S.I. unit lumen (lm).

Screen gain is the reflectance of the projection surface where 1 = 100%, typical of a standard projection screen. Note that higher screen gains are available, however come at the expense of viewing angles, which are typically narrowed with increasing screen gain.

Integration of AETM guidelines with local institutional standards

In order to provide the basis of a clear brief to the requirements of each space, the AETM recommends internal AV system designers work with lighting and electrical teams to integrate the appropriate elements of this section into your local institutional lighting and electrical standards, as well as provide a reference for further information. This will ensure project teams are aware of the requirements in presentation spaces, and that they are well defined in early-phase contractual project documentation.

The AETM also recommends that internal standards require lighting designs for presentation spaces with AV be signed off by the appointed audiovisual designer. This will ensure lighting and electrical designs are considered early, and are fit-for-purpose to support the types of AV systems being deployed on a project, optimising system performance and user experience.

Ratio of Projected Versus Ambient or “Spilled” Light

The clarity of projected images relies on a sufficient contrast ratio between the light from the projector and the ambient or spilled light falling on the projection screen. AETM endorses the ANSI/INFOCOMM 3M-2011: Projected Image System Contrast Ratio as the basis of this performance criteria. As these standards apply to the tertiary environment, we can identify three situations:

  1. Projection of Text and Graphics (e.g. PowerPoint Slides or image from a document camera) where it is expected that reasonable ambient light levels are provided for note taking.

  2. Projection of detailed graphs and photographic images (including medical images and x-rays) where note-taking is secondary to a high contrast ratio projected image which allows for the reproduction of detail in the darkest areas of the picture.

  3. Projection of moving images (film and video) where note taking is secondary to a full contrast ratio projected image which allows for the appreciation of detail in both the brightest and darkest scenes in the presentation.

It is the responsibility of the lighting designer, working with the audiovisual designer, to ensure that ambient light from all sources is sufficiently controlled so that the minimum recommendations regarding contrast ratio are achievable at any point on the image area.

Control of ambient and spilled light falling on the projection screen is essential in all spaces with projection, but it is absolutely critical in larger venues. Large venues require large screens which in turn require powerful projectors. For example, using the inverse square law we know that a screen twice the width requires a projector 4 times as powerful to achieve the same brightness on the screen. In general, the audiovisual designer will declare the target illuminance in lux that the projector is able to achieve given the screen size.

Compared with classroom situations described above, the projected light reflected off the screen will often be substantially reduced in these larger venues. Therefore to retain a sufficient contrast ratio between projected and ambient light the ambient light falling on the screen the lighting designer must take particular care with the directional control of light fittings and the control of external ambient light sources such as daylight.

Light coloured floor coverings and furniture (e.g. a lectern) near the projection screens should be avoided as much as possible since they will reflect significant amounts of light from the spot and stage lights onto the screens.

In practice, the lighting designer will ascertain appropriate lighting levels by referencing both the relevant national standards as well as local institutional standards. This section provides guidance on integrating typical audiovisual requirements into such institutional standards, augmenting national standards for modern teaching facilities and technologies.

This section will provide guidance as to typical lighting scenarios in the presentation spaces of tertiary educational institutions. In defining these scenarios by presets we can simplify the communication of performance requirements to lighting designers and programmers.

The following example uses the principles as they apply to individual elements and can be applied to any space supporting presentation using audiovisual systems.

For a typical lecture theatre, four lighting presets are typical, as well as an “Off” setting, and they relate directly to the viewing categories and contrast ratios previously defined:

  1. Preset 1 - “All On” setting. Used for writing on white boards and demonstrations that do not require other visual presentation technology.

  2. Preset 2 - Presentation of Text and Graphics or “Basic Decision Making” (15:1)

  3. Preset 3 - Detailed graphical and pictorial projection or “Analytical Decision Making” (50:1)

  4. Preset 4 - Full motion video (‘cinema’) projection. Where projection takes precedence (with safety and egress lighting) where light for note-taking is only implemented if achievable without excessive spill (>80:1)

In addition, the following measurement points are defined:

  • At the surface of each student writing surface (horizontal plane)

  • In the presentation area (horizontal and vertical planes)

  • On the whiteboard writing surface where fitted (vertical plane)

  • Spill and ambient light on the projection surface (vertical plane)

  • Stair treads and safety lighting (important for safety, rather than AV applications)

Measuring Ambient Light

Where a space exists and is set for refurbishment, illuminance measurements are vital to ensure that an appropriate projector can be selected to meet the contrast ratio requirements in the space at each preset. These measurements should consider the ability of the room as a whole, including lights, blinds and other sources of light that may impact a projected image. Where it is clear that ambient light mitigation (both artificial and natural) is required, it is important to raise in the early phase of a project to ensure that the project manager and stakeholders can clearly understand what is required to make the venue fit-for-purpose, as well as the associated costs.

Whilst it is ultimately the role of the engaged managing contractor to deliver to the organisational standards, guidance from the AV designer on the project is crucial to maximising success of the installed system and discussions between all parties should begin from the first site inspection. Failure to engage in discussions around lighting early can cause significant cost impacts later in the project, and will likely result in a space that is not fit-for-purpose.

System Contrast Ratio Examples:

Target Projected Lux = 500+

Screen Gain = 1

Example A: Whiteboard / Blackboard or Demonstration Mode

Intent:

The lighting (and external light control) must be capable of providing suitable light levels at student writing surfaces to facilitate detailed note taking while simultaneously providing good visibility of notations being made on the whiteboard and/or of the presenter undertaking a physical demonstration in the presentation area together with a safe level of access light. Projection is generally not required in this mode so there is no specification for contrast ratio on the screen.

Design Lighting Levels

  • Note taking light in a student seating area shall be capable of producing between 150 (minimum) and 320 maintained lux (preferred) measured on the horizontal surface of each student writing bench.

  • Separately controllable illumination of presenter to a minimum of 150 lux measured in a horizontal plane and a minimum of 150 lux in the vertical plane within the defined presentation area. Where frontal lighting is used it should be implemented in such a way as to avoid undue glare in the presenter’s field of view.

    • Where video conferencing and/or live camera recording is required, a vertical illuminance of ~450 lux is recommended.

  • Separately controllable illumination of the whiteboard or blackboard area. Lighting to be as even as possible across the surface and should not vary by more than a ratio of 3:1 from brightest to darkest point within the board area with board lights, presenter lights and note taking lights all ON at nominal levels. Lighting must not produce glare or hot spots on the surface of the whiteboard. The average level of illumination on the board with the board lights ON should be 300 lux.

  • While the amount of spill light on the screen from all sources is not defined in this mode, if there is a requirement for projection to be simultaneous with board or demonstration lighting, then spill light on the screen shall be limited so that a contrast ratio of 7:1 is achieved between the level of white illumination produced by the projector across the entire screen surface and the level of ambient light incident on the screen.

  • Stair lighting: refer to applicable Australian standard or local specification

Example B: Text and Graphics Projection Mode (with note taking)

Intent:

The lighting (and external light control) must be capable of providing suitable light levels at student writing surfaces to facilitate detailed note taking while simultaneously providing good visibility of the presenter, a safe level of access light and adequate (15:1) contrast ratio on the screen.

Design Lighting Levels

  • Note taking light in a student seating area shall be capable of producing 150 maintained lux measured on the horizontal surface of each student writing bench and shall have dimming control allowing adjustment down to 10% of full brightness with no noticeable flicker. This lighting source must be controlled to minimise spill onto the projection surface (see below).

  • Separately controllable illumination of presenter to a minimum of 150 maintained lux measured in a horizontal plane and a minimum of 150 maintained lux in the vertical plane within the defined presentation area.

    • Where video conferencing and/or live camera recording is required, a vertical illuminance of ~450 lux is recommended.

    • Where frontal lighting is used it should be implemented in such a way as to avoid undue glare in the presenter’s field of view (see “presenter lighting” section).

  • Whiteboard surface illumination is not required in this mode.

  • Spill light from all sources to be limited so that when note taking light of 150 lux is achieved in the audience area, a contrast ratio of 7:1 is achieved between the level of white illumination produced by the projector across the entire screen surface and the level of ambient light incident on the screen.

The specific expected white level from the projector should be confirmed prior to lighting design. However, as an example, where 500 lux is achieved as projected peak white, spill light from all sources must be <72 lux at any point within the image area of the screen.

  • Stair treads: refer to applicable Australian standard or local specification

Example C: Pictorial Content or Detailed Projection Mode (with note taking)

Intent:

The lighting (and external light control) must be capable of providing suitable light levels at student writing surfaces to facilitate note taking while simultaneously providing good visibility of the presenter, a safe level of access light and adequate (50:1) contrast ratio on the screen.

Design Lighting Levels

  • Note taking light in a student seating area shall be capable of producing 50 maintained lux measured on the horizontal surface of each student writing bench and shall have dimming control allowing adjustment down to 10% of full brightness with no noticeable flicker. This lighting source must be controlled to minimise spill onto the projection surface (see below).

  • Separately controllable illumination of presenter to a minimum of 50 maintained lux measured in a horizontal plane and a minimum of 50 maintained lux in the vertical plane within the defined presentation area.

    • Where video conferencing and/or live camera recording is required, a vertical illuminance of ~450 lux is recommended.

    • Where frontal lighting is used it should be implemented in such a way as to avoid undue glare in the presenter’s field of view (see “presenter lighting” section).

  • Whiteboard surface illumination is not required in this mode.

  • Spill light from all sources to be limited so that when note taking light of 50 lux is achieved in the audience area, a contrast ratio of 50:1 is achieved between the level of white illumination produced by the projector across the entire screen surface and the level of ambient light incident on the screen.

The specific expected white level from the projector should be confirmed prior to lighting design. However, as an example, where 500 lux is achieved as projected peak white, spill light from all sources must be <10 lux at any point within the image area of the screen.

  • Stair lighting: refer to applicable Australian standard or local specification

Example D: Full-Motion Video Mode

Intent:

The lighting (and external light control) must be capable of providing adequate (80:1) contrast ratio on the screen, along with a safe level of light for egress. It is generally accepted that note taking light is not required within this scenario.

Design Lighting Levels

  • Spill light from all sources to be limited so that a contrast ratio of 80:1 is achieved between the level of white illumination produced by the projector across the entire screen surface and the level of ambient light incident on the screen.

  • The specific expected white level from the projector should be confirmed prior to lighting design. However, as an example, where 500 lux is achieved as projected peak white, spill light from all sources must be practically eliminated at any point within the image area of the screen top achieve 80:1.

  • Practical note taking light in a student seating area will be almost impossible to achieve. If note taking light cannot be achieved without any compromise to the amount of spill light on the screen, then note taking light should be eliminated.

  • Presenter illumination is not required in this mode.

  • Whiteboard surface illumination is not required in this mode.

  • Stair lighting becomes critical for safe egress: refer to applicable Australian standard or local specification.

The table below provides an example of the indicative maximum ambient/spilled light limits for different screen sizes based on projected lux levels. In all cases, the actual contrast ratio shall take precedence.

Common projected vs. ambient lux scenarios

Room Type

Screen Size

Projector ANSI

Lumens

Non-Std Lens

Typical Projected LUX

Max Ambient Light on Screen (lux)

Text

Max Ambient Light on Screen (lux)

Photo

Max Ambient Light on Screen (lux)

Movie

Meeting room

100"

~3,000

no

600641

8543

4012.8

128

Small Seminar room

115"

3~4,000

no

450782

6552

3015.6

99.8

Large Seminar room < 11m

130"

4>5,000

no

575765

8251

3815.3

119.6

Lecture Theatre >11m

150"

5~7,000

yes

465644

6643

3112.9

98

Auditorium

200"

7500>10,000

yes

385517

5534

267.7

84.8

This is a guide only – figures will vary depending on lens type, illumination source and other factors. Calculations should always be performed on a ‘per installation’ basis.

Lighting Zones and Circuits

Small to medium-sized projection-based learning spaces

Small to medium-sized teaching and presentation spaces with projection typically require three lighting circuits/groups at a minimum to allow sufficient zonal control for appropriate lighting levels on subjects and task areas whilst avoiding spill on projection surfaces. Each of the circuits should be independently dimmable to allow fine tuning of light levels during commissioning, as well as functional operation of the space. Other zones/circuits may be used if required, and these should be switched and/or dimmed separately if they have the potential to impact the projection system.

Provide separate light fittings and logical or physical switching circuits for:

  • Front/board lights for illuminating vertical writing surfaces. Where multiple independently controlled screens are used, consider additional board light zones for maximum flexibility, allowing simultaneous whiteboarding and projection in some applications.

  • Directional lighting to illuminate the presenter at the lectern and other presentation positions (e.g. “stage” areas) without spill on the screen

  • Audience area lights provided for note taking

Directional lighting of the presentation area is a strongly recommended feature suitable for all venues that use projection. Without it, the presenter will either need to be in the dark while presenting or they will turn up the board and audience lights, washing out the projected content and making it difficult for learners to assimilate information. Further information is available in this section related to lighting presentation areas.

The illustration below is a typical three circuit layout consisting of separate lighting fixture types and control circuits for board lights, presenter lights and audience lights (used for note taking). Note that in small rooms, even if specific board lights are not used, it may be necessary to isolate the lighting nearest the screen surface so that it may be switched off during projection without affecting the note taking lights over the general audience area.

graphical depiction of three circuit lighting including board, presenter and audience lights

Graphical depiction of three circuit lighting including board, presenter and audience lights

Small to medium-sized learning spaces fitted with flat panel displays

All the above concepts hold true when using flat panel display technology, however the need to control the spill of light is not as critical, nor is the ability to fine tune to the levels.

Whilst it is good to adhere to the above principles in these spaces, it is recognised that often a simpler system is acceptable, in order to keep costs at a reasonable level (particularly in smaller spaces).

It is worth noting that whilst light falling onto a screen is not such an issue when using flat panel displays in this context, ‘glare’ caused by reflections most certainly can be. When the lighting is designed it must be ensured that in reference to the presenter and audience positions, the selection and positioning of light fittings with regards to flat panel displays avoids causing specular reflections which will vastly reduce the system contrast ratio and legibility.

Lecture theatres and larger presentation spaces with projection

Larger venues and those with higher complexity of use often have sophisticated requirements extending beyond the three zone scheme used in smaller teaching spaces. All zones must be under the control of the presenter via presets, with the exception of exit, stair tread/aisle and safety lights (which may be required to be always on). Access to dimmer controls are often also provided, as this allows the presets to be tweaked to the user’s specific requirements.

Provide separate lighting zones, appropriate fittings and logical switching circuits for:

  • board lights (as required)

  • directional lighting to illuminate the presenter at the lectern and other presentation positions (e.g. stage left, centre, right areas) without spill on the screen.

  • multiple audience lighting zones, grouped from front to rear of audience, rather than across the width of the space for optimal control

  • aisle lights, safety and exit lights

  • other zones/circuits as required (e.g. for demonstration or performance spaces)

Lighting the Presenter

Presentation areas should include at a minimum, ‘key’ and ‘fill’ lighting, to ensure that the presenter’s face is well illuminated and shadows are minimised. This affords an improved ability for all audience members to visually correlate spoken word which is of critical importance to persons who are hard of hearing. In dedicated video conferencing and event spaces, ‘back’ lighting should also be employed to ensure the presenter stands out against their background.

Key, Fill and Back Lighting - the basic ‘three-point’ lighting concept

In a world with an ever-increasing number of live video streams, conferences and capture applications, it is important to ensure that a person stands out against their surroundings to create a clear and dynamic representation of them for all audiences. The three-point lighting method has long been used to achieve a three-dimensional look in media production and event lighting, and is a good practice to use when lighting presentation areas to increase the quality of video capture as well as the learning experience of the audience. Three point lighting has three elements - key, fill and back light.

Key-lighting is typically the primary and brightest light source used on a presenter’s face. It should be placed to illuminate the presenter’s side that is predominantly facing the camera or audience. It’s angle should be approximately 45 degrees diagonally to the side from the direction the presenter primarily faces, and elevated 50-60 degrees from their horizontal eye-line to strike a balance of illumination, shadow creation and glare control, the latter of which can be very uncomfortable when presenting.

Fill-lighting is next and is used to ‘fill’ in the shadows created by key lighting. It should be angled closer to the axis of the camera or audience location and its intensity curtailed so as to avoid creating another set of shadows. A ‘softer’ light is recommended for this function where feasible. Again, it’s angle should be in the range of 30-45 degrees from the direction he presenter primarily faces

Back-lighting is the final element, and is what creates the look of depth of a subject against a two-dimensional background. Backlighting is placed behind a presentation area, can be positioned higher and often on steeper angles than other fittings as the aim is to primarily highlight the top of head and shoulders of a presenter. The rear light can also be targeted from the rear and to the side, often aligned with the axis created between the key light and presentation area. This particular rear lighting arrangement is often called a ‘kicker’ or ‘clip’, and its use allows some flexibility when working with presentation areas that are in front of displays and projection screens, although its ability to backlight a person is limited to the side and features it is able to throw light upon from its position.

Light Fitting Selection

Light fittings, accessories and their configuration are the tools required to achieve the performance criteria set out in this document and standards. Their directionality, luminous intensity, Unified Glare Rating (UGR) and ability to render colours correctly are all factors that must be considered to achieve these stated design requirements. By taking a ‘performance requirements’ approach, we can simplify the extent to which AV designers need to concern themselves with the specifics of the light fittings, which is ultimately the responsibility of another professional on the project - the lighting designer. This section aims to cover the basic considerations to take into account when reviewing lighting designs and fittings specified by the lighting designer.

Light fittings with good directional control are required to eliminate glare and unwanted lighting spill on display devices. The closer the lights are to the projection screens and displays, the more important this requirement becomes.

Light fittings without horizontal shielding and louvers, or light fittings that bounce light off ceilings or other surfaces do not provide sufficient directional control and are generally not suitable for spaces with projection. Low brightness non-reflective louvers are preferred.

During a presentation different lighting settings may be required in rapid succession. It is essential that the lights used be capable of being switched on and off (or dimmed) quickly. Lighting technologies which require long delays between extinguishment and re-strike, or fittings which take more than 10 seconds to achieve maximum brightness are not suitable for general purpose teaching spaces.

General Light Fittings Compatible with Projection

To minimise ambient light spill onto projection surfaces, light fittings of a glare free design with direct light distribution only (i.e. no upward incident light) should be used. These often have reflectors with cut-off or shielding angles of 50 degrees or less in the direction of the screen(s). Recessed lights with non-reflective louvers or suspended lights with sufficient side shielding reflectors and non-reflective louvers are usually suitable.

Providing the lighting designer the system contrast ratios as target performance criteria is the best way to achieve the required results without dictating specific brands or technologies.

zumptobel light graph

Shown above is an example of a louvered fitting suitable for use in rooms with projection along with a typical dispersion pattern

Task lights and spotlights that are required for presenter areas during projection must be designed to avoid spill on projection screens. They often have several options available to control the light dispersion, including internal cutters, lenses or external barn doors to enable illumination of people near the screen, while preventing direct light falling on the screen.

Again, using the required system contrast ratio as the performance criteria for a design is the best way to achieve the required results without dictating specific brands or technologies to the lighting designer. Using an illuminance meter on site during commissioning or in reviewing the installation can be used to determine if the contrast ratios PL-1-track-barn-door_No-BG_Greyscale

Example of an LED Spotlight light fitting which provides the beam control needed for presenter lighting without excessive spill.

More compact units are also available.

Light Fitting Placement

The placement of lights in relation to the projection screens is another critical aspect of lighting design for teaching and presentation spaces.

As previously mentioned, house lights, stage lights and lectern spotlights must all be carefully positioned to avoid spill on the screen, taking into account their beam cut-off/shielding angles. This can be confirmed by computer modelling during the design stage and should not be left until the lights are installed.

Care must also be taken when placing light fittings to ensure that subsequent to their final alignment the body of the unit does impede a projector’s light path. This is particularly the case with spotlights, which are often positioned at a significantly downwards angle.

The vertical positioning of stage lights and lectern spotlights is often a difficult balance between providing sufficient light on the presenter’s face and avoiding glare in their eyes. A commonly agreed balance is to position these lights between approximately 50 degrees and 60 degrees above the horizontal from the presenter’s eye-line.

Board lights should be set back from the boards a sufficient distance to allow even coverage.

House Lights

House lighting shall be directional in nature, dimmable, low spill, low glare, even and reasonably shadow-free providing approximately 320 lux falling on audience horizontal reading surfaces when operated at 100%.

Fluorescent light fittings should be of ‘rapid-start’ energy efficient type with no flciker and zero audible noise. They shall met the stringent low glare and spill requirements described in the previous section - Light Fitting Selection

Board Lights

Whiteboard lights are essential for the visibility of the whiteboard. Light levels falling on the board must at least match the levels on the reading surfaces of the audience section.

A common mistake is to mount the light directly above the board. This approach will result in a hotspot at the top of the board and ineffective lighting towards the bottom. A more successful approach is to position an asymmetric “wall washer” light fitting some distance out from the boards and to have its light angled across the full height of the board. There is a range of specific fixtures for this purpose.

Lighting should be as even as possible across the surface and ideally will not vary by more than a ratio of 3:1 from brightest to darkest point within the board area with board lights, presenter lights and note taking lights all on at nominal levels. The average level of illumination on the board with the board lights on should be 300 lux. Board lighting must be separately controllable.

wallwash

Example of a recessed asymmetric wall washer

Stage Area Lights

Whether to illuminate presenters as they move around the room or for a table of speakers at a conference, ‘Stage Lighting’ provides a means of illuminating the required presentation area while avoiding washing out the projected images.

Stage lights must be dimmable narrow-beam directional lights with excellent control of spill. They should include devices such as barn doors, lenses or cutters to accurately shape the light beam to avoid spill on the projection screen while at the same time lighting as much of the area in front of the screen as possible.

For smaller venues the principle of providing lighting with strong spill control near the screen is just as valid. In this context it may be achieved with a series of small downlights or directional fluorescent/LED lights with highly effective louvers.

Presenter Spotlights

In lecture theatres and large venues a minimum of two narrow-beam focussing spotlights should be installed to light the presenter at the lectern. The spotlights would normally require full beam control (zoom, focus and cutters or barn doors) to adjust the light coverage and minimise spill onto the screens. PArticular care should be taken to avoid reflections off the lectern surfaces. For large venues theatrical spotlights are suitable.

In smaller venues a range of cost effective low voltage fittings can be used. A compact fluorescent asymmetric wall washer recessed in the ceiling can also be effective as long as care is taken to position it well and direct its beam well clear of the projection screen.

Aisle Lights

When installed, aisle lighting must meet the relevant building codes in terms of edge and step definition. The selected aisle light fittings must emit no, or minimal spill onto projection screens. A range of LED based lights are available that provide both edge definition and tread illumination.

Exit lights

Special consideration should be given to the type and location of exit lights in lecture theatres and performance venues. Exit lights can have a detrimental effect on projection quality by producing an unacceptable level of ambient light.

Projection booth lights

Many large lecture theatres are equipped with a projection booth (otherwise known as a ‘bio box’). A bio box should have as a minimum the options of good general lighting for when the theatre presentation space is unoccupied, as well as separate highly directional downlighting for the provision of working in the space when a presentation is underway. These lights need to be operable independently of the venue’s lighting control system, from within the booth.

Control of External Ambient Light

With the continued prevalence of glass facades in new buildings, architectural design of teaching spaces with projection systems must be approached with special consideration to ensure the appropriate controls are in place to mitigate natural light, partiularly from windows and skylights.

The space planning phase (a.k.a “blocking and stacking”) should be used to ensure the placement of sensitive projection spaces (e.g. cinemas or video conferencing spaces) within the internal areas of a building.

Where windows or skylights are unavoidable, use of curtains or blinds and louvers to control ambient light will be required. Motorised control of blinds or louvers are always preferable to support projection systems as they provide the easiest means of control for the user, cater for automation based on presets, and can minimise the wear and tear often associated with manual operation.

For video conference rooms complete control of sunlight is essential. Even small gaps in curtains can severely reduce the quality of the image captured by the camera. (See also the Special requirements for Video Conference spaces section below)

IMPORTANT NOTE: Light from external sources should be excluded or controlled so as to allow the attainment of the performance criteria with respect to spill on the projection screen at any time of day and at any time of the year. In other words, the minimum requirement is to meet the criteria in the brightest possible conditions. Many projects have failed because they have used the average figure for the brightness of ambient daylight, instead of the maximum.

Special requirements for Video Conference spaces

Video conference venues are in effect small television studios and require additional care and consideration in lighting design. It is important to minimize shadows, eliminate glare, avoid reflective surfaces and to create an evenly lit environment.

It is best to use lights fitted with diffusers as general lighting for video conference purposes. However, even fluorescent or LED lights of this type will cause unattractive shadows around the eyes of participants if placed directly overhead. When carefully placed, asymmetrical wall washer light fittings can provide an even light at a 45 degree angle that reduces eye shadowing. Carefully applied spotlights can also provide pleasant shaping and highlights to the participant’s faces. For consistency of colour and skin tone reproduction by the camera, use lights of the same colour temperature (e.g. 4000 Kelvin) and ensure illumination of participants' faces is at around 500 lux.

Ideally, the room should not have any exterior windows. If it does, they need to be fully covered with curtains or blinds. Even a small chink of sunlight in the background can cause problems for the camera. Backgrounds and table tops should not be too dark or too light as this can cause difficulty with camera auto-iris control. Mid tones and moderate lighting levels on background walls will give the best results.

Avoid patterned or woven fabrics and finishes on walls as these can produce moiré patterns or strobing effects when the camera is moved.

Control and Automation

Lighting System Integration

Presenters need quick access to flexible but easy-to-use lighting controls located at the presentation position. Best practice is to always integrate lighting control with the room’s AV control system.

In projection-based spaces this is an essential requirement.

Failure to integrate lighting control with the audiovisual system will often result in presentations being washed out as users are not aware that they need to turn the board lights off, or are unfamiliar with the location of the lighting controls.

Integrating with the AV system allows automated selection of the appropriate preset to support a selected functionality within a space. At a minimum, the following is recommended as best practice for AV and lighting system integration:

  • All presets required for teaching are available at the LCP, and available for recall from the AV control system

  • Directional presentation lights should be grouped per presentation area (e.g. lectern, stage right etc.) and included within lighting presets. Specific user controls are recommended to allow optimisation of a lighting scene to suit their needs.

  • Board lighting controls are provided to the user and automatically turned off in association with a presentation mode (defined by the AV control system).

  • Blind controls are available at the LCP, and available for recall from the AV control system.

  • Occupancy sensor flags are available for use by the AV control system to automate system “keep alive” and shutdown states. Coverage requirements will cover the stage and presentation areas at a minimum, and the majority of the audience where feasible.

  • The AV control system is programmed with macros based on the application selected for the AV system (e.g. upon sending content to the projector for the first time, Preset 2 is called, board lights are turned off, presentation lights on, and sheer blinds are dropped, with the aim of achieving a 15:1 system contrast ratio).

Lighting interface for AV control

In order to integrate most lighting systems with AV control, a gateway (also called a ‘node’) between the two systems (typically via serial or network connection) is required.

Interfacing can typically be achieved at a room, group of rooms, level or building, depending on the lighting system design.

An important consideration that will drive the AV requirement is how many simultaneous communication sessions the lighting gateway is able to maintain with a control system, as well as how the control system is programmed to operate. Many lighting control system nodes only allow a single connection from a third-party (AV) control system, so either control code must take this into account, or a node be supplied per AV control system. Three examples are provided to illustrate this point:

  1. Per-Room Deployment

Where AV control processors are deployed on a per-room basis, a lighting node may be required per space to ensure communications between the two services is reliable. Whilst this is the most robust from a redundancy perspective, it has the highest cost, time and hardware requirement.

  1. Building/Campus Centralised

Alternatively, a centralised AV controller processor solution could be used to communicate with a lighting node that accesses all rooms in an area, level or building. This approach is recommended where centralised control across buildings or campuses is leveraged, and saves time and money on installing and commissioning lighting gateways per room.

  1. Per-Lighting Area Deployment

A middle-ground can be achieved by using an intermediary AV control processor to communicate with all of the lights on a particular lighting network, and having other AV control processors “talk to each other”. Coding requirements and standardisation will need to be considered if this approach is taken.

It is important to understand that both scenario #2 and #3 will mean there is a single point of failure for lighting system integration at the level of control you have decided upon, and this will need to be considered and mitigated with any design and/or maintenance planning.

Independent Lighting Control Panels

Independent lighting control must always be provided by a Lighting Control Panel (LCP) so as to avoid a single point of failure for the lighting system, provide a clear distinction between services for support and maintenance purposes, as well as provide a very simple control for users that do not require audiovisual presentation.

Wall mounted lighting control panels (or “Entry/Exit” switches which bring up the appropriate lighting mode) must be placed near entrances in accordance with applicable regulatory requirements as well as building and institutional standards. When the venue has a bio box additional lighting controls should be installed there as well.

Occupancy Detection

Occupancy or motion detection is a common feature of modern lighting systems. It enables significant energy savings by shutting down services when the space is unoccupied for defined periods of time. Occupancy sensors should be installed as part of all new lighting systems. The output of the occupancy sensors should be available to the AV control system and should also provide input to the BMS (Building Management System). This can allow for energy management of both AV equipment, lighting and mechanical services in the space.

To avoid unwanted AV system shutdowns during longer sessions where people may be stationary for extended periods of time (for example during examinations), the sensor technology must be capable of detecting the presence of stationary occupants and not just those traversing the space. Full coverage of the space is preferred to cover situations where spaces are used for the watching of films, or extended student group work sessions using AV.

‘Zero occupancy time out’ events and user initiated lighting and AV system shut down routines must be programmed. The desired lighting and AV system actions at each stage of the routine should be documented and agreed upon by stakeholders.

Dimming

Dimming provides finer control of the presentation environment to optimise the user experience and performance of audiovisual components whilst giving flexibility to meet different user’s comfort requirements. Dimming can also result in more efficient use of energy.

If dimming is required to meet the system contrast ratio performance criteria of a space, it must always be allowed for and installed.

Dimming must only be achieved using appropriate dimming technology to suit the installed light fittings. Care should be taken to ensure that no flicker, audible noise, electronic interference or other undesirable artefact is evident throughout the dimming range.

In some very basic instances an equivalent, albeit rough, dimming effect can be achieved by selective switching of audience light fittings, however actual dimming should always be the preferred method.

Dimmer Location

Digitally addressable dimmers and light fittings are recommended for modern teaching environments.

Dimmers should be located in positions that facilitate easy access. They should not be located in ceiling cavities or in false floors which are difficult to access. Dimmers must be mounted at a height which allows ready access for a standing technician, without using a ladder or having to crouch or kneel down. The operation of the dimmers must not cause electronic magnetic or any other kind of interference with other systems within the room or in the vicinity.

Fire, Emergency, Mechanical Services and BMS integration

Where required by code, the AV and lighting system will need to accept and respond to signals received from the buildings emergency warning system (EWIS). An emergency signal to the system should trigger the actions determined by regulation e.g. turning on the lights for safe egress, muting the sound systems to clearly hear warning announcements etc.

The AV system controller is often a good candidate for receiving this signal as it is able to perform all of the above actions by nature of its connectivity to sub-systems, including lighting.

In many cases it is desirable to connect the room control system to the Building Management System (BMS). This allows the room automation to send signals to the air conditioning regarding lighting states and room occupancy.

In both of the cases above (EWIS and BMS), it is important to work with your facilities management teams to ensure there is a clear understanding of the roles and responsibilities of the various service managers in achieving the overall integration of building services. All systems need to be thought out, mitigated and tested across building services.

Lighting Design Modelling and Calculation

It is a good practice to ensure that all lighting designs are computer modelled during the design stage to ensure that the light falling on the projection screen does not exceed contrast ratio limits and that presentation, board and audience areas are sufficiently lit, in both horizontal and vertical planes, noted earlier in “measurement points”. Local organisation lighting/electrical standards should provide reflectance values, calculation points and methods that are deemed acceptable, and should reference these guidelines, as well as the illuminance levels and contrast ratios required to be achieved. See “calculating the system contrast ratio” for detailed information on how to ensure the projection illuminance is set adequately as the basis for each lighting preset.

If the design does not meet the performance requirement of a space then a review of the light fittings, placement and presets will be required prior to design finalisation. Where spaces are reasonably identical in ambient light profile, a model or calculation may be suitable to cover multiple venues.

When designing spaces that use flat-panel displays, the need for modelling is simplified and often removed due to the inherent high-contrast afforded by the technology. This ensures the lighting designers job of illuminating the presenter is a simpler exercise and can be based on simpler calculation methods to prove that lighting is appropriate. An important consideration in this scenario is ensuring that artificial and natural light sources are controlled appropriately to remove specular reflections caused by very bright windows or overhead light fittings. A simple calculation using trigonometry and the luminance of the source should be used to determine if windows or light fittings are likely to cause an impact from the audience’s location when the display is on, and mitigated in the design where required.

Additional Lighting Parameters

Thus far we have covered the essential considerations for lighting within a presentation space. However, lighting is a complex subject, and lighting professionals exist for a good reason! It is always advisable to consult them when engaging in a project. It is worth being aware that the following parameters may factor into a lighting designer’s recommendations, and are often found on a light fitting’s specifications.

Spectral Power Distribution (SPD)

Visible light that is made up of a spectrum of wavelengths from 380 nm (violet) to 760nm (red). Spectral Power Distribution (SPD) describes the power of each wavelength that is produced by a light source to generate what we perceive cumulatively as white light, usually in the form of a graph.

Luminous efficacy

Luminous efficacy is the sensitivity of the human eye to light, as a function of wavelength (380-760nm) and power (watt). Luminous efficacy is typically represented visually as a graph under both light-adapted conditions (photopic) where it peaks at 683nm/W and dark-adapted conditions (scotopic), peaking at 1700lm/W.

Luminous Efficacy Ratio (LER)

A measure of how well a light source converts it’s electrical energy into light, as a function of the human visual system’s response, also known as the luminous efficacy function.

By way of example, consider two light sources that both require the same electrical energy to run - one that produces large amounts of infrared light with little visible light and another light fitting that is well tuned to the human luminous efficacy function.

The light which is high in infrared will have a low luminous efficacy and not be very efficient for lighting a space for human vision (as well as likely causing interference with any infrared hearing augmentation systems).

Universal Glare Rating (UGR)

Glare in a person’s field of vision can cause visual discomfort and reduce their ability to perform visual tasks. Glare is most often caused by bright sources of natural or artificial light and can also be due to reflections from specular surfaces. Universal Glare Rating (UGR) is described by a CIE standard as a measurement of the glare of a light fitting.

For office tasks which include typical educational environments, a UGR of <19 is recommended. For complex visual tasks such as detailed inspection or laboratory work, a UGR of 16 (the lowest rating) is recommended.

Colour Rendering Index (CRI)

Originally developed by the International Commission on Illumination (CIE) in the 1930s and updated in the 1970s, the Color Rendering Index (CRI) was the first industry standard for measuring how color appeared under different light sources. It is defined as a number between 0-100, where >90 is considered “excellent” and <80 is considered poor.

CRI will eventually be replaced by other standards (see TM-30) within lighting markets as it is limited to a light’s ability to reproduce only a limited number of colour samples; a high score does not specifically mean that a light fitting is better in terms of colour rendering performance overall.

TM-30

Similar in purpose to CRI, the TM-30, last updated in 2018 (TM-30-18) is a standard developed by the Illuminating Engineering Society (IES) for measuring the colour rendering of a light fitting. It is often found next to CRI data on a specification sheet, and expands upon CRI to provide multiple dimensions that describe a light’s colour performance which is particularly helpful for LED lighting:

Fidelity Index (Rf) - colour rendering performance with reference to daylight (score of 0-100)

Gamut index (Rg) - intensity of colours with reference to daylight (score of 0-100)

Vector Graphic - level of saturation/desaturation of certain colours (represented as a 2D colour spectrum with reference/test circles)

TM-30 Vector Graphic example - Image sourced from https://amerlux.com