Environmental Considerations and Human Factors for Videowall Design

The ability to present clear, high quality imagery from multiple sources and at large sizes makes videowalls valuable for maintaining situational awareness, as mission-critical information is presented in a working environment such as a control center. In public spaces, videowalls can deliver visual impact and effective messaging in entertainment and promotional applications. An effective videowall will be properly integrated into its physical environment, and be engineered for efficient, ergonomic use.

An effectively designed videowall system, with proper consideration for environmental and human factors, ensures viewing comfort and optimal accessibility for everyone in the room. This in turn helps to maximize the value and effectiveness of the videowall in conveying visual information.

When designing a videowall system, individuals frequently begin by focusing on the most visible element, the displays. However, to properly determine which display technology and specifications are best for a given installation, physical and operational dynamics must be considered as part of a complete AV system design. Ignoring the environmental and operational requirements can lead to less-than-optimal results for a high value videowall, in what could otherwise be an outstanding system design.

Many environmental and human factors, as well as ergonomic engineering essentials seem obvious when considered after the fact. Unfortunately, AV designers are often not involved early enough in a project’s life cycle to prevent all possible shortcomings regarding these important details. Preparation of two-dimensional plans and section drawings are essential to reviewing the physical considerations for the environment. 3D visualizations, such as in Figure 2-1 , can also be valuable for pointing out environmental concerns to end users and project stakeholders with limited experience in videowall applications.

An effectively designed videowall system, with proper consideration for environmental and human factors, ensures viewing comfort and optimal accessibility for everyone in the room. This in turn helps to maximize the value and effectiveness of the videowall in conveying visual information.

A great deal of government, academic, and commercial research has been conducted in the area of human factors and ergonomic design for control centers. The International Standards Organization - ISO has published standard 11064-1:2000 for ergonomic design of control centers, and the US military has established standards for human engineering that addresses use of visual displays.

The human factors and environmental considerations presented here are specific to videowalls for control room environments. The same concepts can be applied to other applications where videowalls may be used.

Viewing Locations

It is essential that all the intended users can easily view the videowall. When evaluating horizontal and vertical viewing angles, the following questions should be answered:

• Where are the primary viewers situated relative to the videowall?
• Are there any secondary viewing locations for individuals not directly engaged with the display? Examples of secondary viewing locations include viewing galleries or management offices.
• Are there any physical barriers that could obstruct the videowall for some users?

In large rooms, such as a control center, viewing locations will vary greatly. It is important to evaluate viewing angles in both the vertical and horizontal planes. If physical barriers are identified, additional displays may be required to expand the videowall, or extra localized displays may be necessary. Some environments may require that the videowall be split into smaller systems to sufficiently cover all viewing areas. In other cases, adding curvature to the videowall layout will improve viewing coverage, as illustrated in Figure 2-2.

Eye and Head Tilt

In control rooms, operators typically manage tasks using one or more local flat-panel displays while monitoring content on a videowall positioned beyond their workstation. Eye and head tilt between workstation displays and the videowall should be compared against recommended human engineering standards for visual field of view, eye rotation, and head tilt. Proper consideration for eye and head tilt ensures comfortable viewing for users as they alternate between their workstation displays and the videowall. This analysis should always be performed for control rooms, whether information is to be presented on a videowall, individual wallmounted displays, or a large screen. See Figure 2-3 and 2-4.

A similar field of vision, eye rotation, and head tilt analysis should be applied when a videowall is designed into a public or entertainment venue. Personal displays may not need to be considered, but the design must offer comfortable viewing from seated or standing positions.

Display Size and Legibility

Minimum requirements for display dimensions or the size of individual image windows will be driven by viewing distances. The viewing distance will also be critical when considering the display resolution and pixel density of information presented on the displays, as well as the sizes of characters and symbols. "Choosing the right Videowall Shape and Size" and "Font Size and Legibility for Videowall Content" cover these topics in more detail.

Advancements in lamps and LED illumination sources have made LCD panels, projection cubes, and high brightness projectors suitable for use in bright ambient light environments.

The Physiology of Color Vision

When preparing content to be presented on a videowall, it is important to have a basic understanding of human vision and the physiology of color. Proper use of color can enhance a viewer’s ability to interpret data, while improper use of color can result in eye strain. Text, data, or visual symbols should be presented applying a background using a complementary color. See Figure 2-5.

Display Brightness

Images produced by videowalls must be sufficiently bright, so that they can be clearly visible. Today, many work areas with videowalls employ lighting designs that produce an abundance of ambient light, and may include outdoor windows that contribute natural light. Fortunately, advancements in lamps and LED illumination sources have made LCD panels, projection cubes, and high brightness projectors suitable for use in bright ambient light environments.

Display technologies continue to evolve, offering improvements in brightness, resolution, contrast, form factor, power consumption, or cost efficiency. Whatever display technology is being considered, it is always important to use professional methods for defining display brightness requirements that include ambient light conditions.

Ambient lighting conditions are determined in terms of illuminance, which is a measurement of all light sources illuminating a point on a surface. Illuminance is measured in lux - lx, equivalent to lumens per square meter - lm/m2. Wherever possible, determine the ambient lighting for a site by referring to the facility’s lighting design specifications, or visiting the site and taking measurements once the lighting has been integrated. Table 2-1 lists typical illuminances for various environments.

Illuminance calculations are regularly prepared when planning front projection systems. The illuminance produced by a projector can be calculated by dividing the projector’s ANSI lumens output by the screen’s surface area, in square meters. The result can then be compared with the ambient light levels in the room. A projector’s light output in ANSI lumens is usually listed under “Brightness” in projector specifications.

Flat-panel displays and projection cubes also identify luminance values as “Brightness” in their specifications. However, they are quantified as nits or candelas per square meter - cd/m2. Luminance describes the amount of light leaving a surface in a specific direction. See Figure 2-6. In terms of measurement, one cd/m2 is the equivalent of one lux at a defined direction. Specifications of brightness or luminance for flat panels or projection cubes identify values that are on-axis or directly perpendicular to the screen.

Projection cubes and flat panels with luminance values between 300 and 1,000 nits provide adequate brightness in control room as well as office environments. Projection cubes that have been designed with diagonal screen sizes beyond 80 inches (200 cm), or those that have been engineered to offer extended lamp life may have specified luminance values below 300 nits. Use of these displays requires greater attention to ambient light conditions and lighting designs. Table 2-2 lists typical luminance ranges for various display types.

For a projection cube, on-axis luminance is determined by measuring or calculating the illuminance – projector ANSI lumens divided by screen area, and then multiplying this result by the gain of the projection screen. Rear projection screens with high gain typically yield lower luminance values at off-axis viewing angles. This reduction in brightness helps to illustrate the significance of the direction of light for luminance. Projection cube specifications usually identify the horizontal and vertical viewing angles at which the luminance will be one-half, or a lower percentage relative to the on-axis value.

Luminance is also important for large-screen rear projection systems. System designs must include proper specifications for projector ANSI lumens, screen size, and screen gain to ensure sufficient luminance within the ambient lighting conditions of the environment.

Some display manufacturers continue to list illuminance and luminance specifications or calculations based on English standard units using square feet rather than square meters. Conversion factors from lux and nits to footcandles and foot-lamberts are listed in Table 2-3.

Table 2-3. Conversion factors for brightness values derived from metric and English standard measurements

In addition to brightness, videowall displays must offer sufficient contrast, so viewers can easily distinguish text, data, symbols, and visual details in video or graphic images.

Display Contrast

In addition to brightness, videowall displays must offer sufficient contrast, so viewers can easily distinguish text, data, symbols, and visual details in video or graphic images. A display’s contrast ratio describes the dynamic range it offers for presenting imagery, from deep blacks to peak whites. Contrast ratio is a measure of the ratio between the brightest and the darkest luminance values produced by the display. Higher contrast ratios are commonly associated with greater subjective picture quality.

High brightness contributes to a higher contrast ratio by increasing the white measurement. However, producing very high contrast ratios requires even greater attention to reducing dark values. For product specifications, contrast ratio is based on measurements taken in a completely dark room. Unless the display is to be used in a similarly darkened environment, contrast ratio product specifications should not be factored too heavily when comparing products. The standard method for determining contrast ratio is illustrated in Figure 2-7.

Brightness and contrast can be objectively determined with light meters, but in the end, customer satisfaction can be purely subjective.

Many direct-view flat panels include high contrast surfaces to disperse incident light and reduce reflections on the screen. Front and rear-projection screens include various coatings or tinting to diffuse incident light and improve contrast. In control rooms with projection systems, contrast is frequently optimized by formatting data and graphic content with dark backgrounds and bright characters or symbols, and maintaining low ambient light conditions. For direct-view panels, content frequently appears better when formatted with bright or white backgrounds and dark characters or symbols. Both types of formatting work well for projection cubes.

In 2011, InfoComm International published standard 3M-2011 for contrast ratios of projected images for different viewing applications. The following recommendations were established: a minimum contrast ratio of 7:1 for images produced purely for informational purposes, at least 15:1 for basic decision-making, 50:1 for critical decision-making, and 80:1 for presentation of full-motion video content.

Introduction of the 15:1 ratio for basic decisionmaking resulted in notable industry feedback, considering that a contrast ratio of 10:1 had been applied as a rule of thumb by industry professionals for many years. Nevertheless, the economic and environmental factors encountered on every project produces challenges that may or may not support attaining these standards.

Brightness and contrast can be objectively determined with light meters, but in the end, customer satisfaction can be purely subjective. There is no substitute for visually evaluating a display’s brightness and contrast in the actual facility it was designed for, or under comparable environmental conditions, using visual content representative of the intended application.

Ambient Lighting

Ambient lighting conditions will impact the resulting contrast, or how images appear under actual lighting conditions. Excessive lighting in a room will conflict with the displays, reducing contrast and making the image appear “washed out” and difficult to view.

The following are best practices for improving the impact of lighting on AV systems in control centers:

• Control ambient brightness throughout the room, minimizing it wherever not essential to human activity.
• Use directional overhead spotlights where possible to keep lighting away from the videowall.
• Incorporate individualized task lighting for workstations, rather than relying on lighting fixtures which apply broad coverage throughout a room.

The following should be avoided:

• Placement of ceiling lights in close proximity to displays; light may spill onto the screen surfaces.
• Untreated windows directly facing a videowall display, particularly those with a southerly exposure.

Note: In northern latitude locations, there have been instances of poor planning for ambient lighting conditions. Specifically, these have been for corporate lobby videowall installations that face windows with a southerly exposure. During afternoon hours in winter months, light from the sun can fall directly onto the displays, significantly reducing their effective contrast.

Wall and Room Treatments

Walls surrounding a videowall should be visually neutral to avoid distracting from the information presented on the displays. See Figure 2-8 as an example. Wall surfaces should have matte finishes and be pattern-free, without windows, open doorways, and other visual distractions, whenever possible. Similarly, ceilings, floors, and facing walls should have matte or nonreflective finishes, and be void of windows and other reflective surfaces, which can result in light falling onto the videowall screens. Wherever windows cannot be avoided, shades and tinting can be used to reduce the impact of exterior light. Acoustic treatments may also be required to control sonic reflections and ensure a quiet acoustical environment where normal conversations can be conducted.

Clocks and Status Indicators

Control rooms, sales or trading areas, and other working environments with videowalls often use world time-zone clocks or system status indicators, such as those which display security conditions. See Figure 2-8. This information may be presented on the videowall, specialized fixtures, or auxiliary displays.

Furniture and Personal Environment Management

Furniture and consoles used in command and control centers are available in standard designs supporting many different workflows. Custom consoles can be designed to support specific working conditions and environments. See Figure 2-9. They may include motorized height settings, highly adjustable seats, task lighting, localized white noise, or local airflow and temperature control for users working in 24/7 operations.

Entry Management and Security

Control rooms and facilities with high-impact displays may have controlled visibility or access for security reasons, or to enhance the visitor experience. For example, an executive presentation room may double as a viewing gallery, with motorized shades or controllable privacy glass to expose an adjoining control room. Control rooms used for customer demonstrations or promotional applications may incorporate a special entryway that includes lighting and AV effects to help shape the visitors’ state-of-mind before they enter the space. This approach is similar to the use of pre-shows in theme park attractions.

The earlier an AV designer participates in the facility design, the greater the likelihood human factors and environmental considerations will be successfully addressed.

Planning Ahead for Effective Videowalls

All of these human factors and environmental considerations can have a significant impact on the effectiveness of a videowall display system. The earlier an AV designer participates in the facility design, the greater the likelihood these elements will be successfully addressed.