GETTING THE PICTURE A visual hierarchy

Howard Brandston was a colleague of mine for some years at the Lighting Research Center, and on several occasions I witnessed him sitting through a student presentation of a lighting design proposal where the student would give a detailed explanation of lamps, luminaires and controls. After a pause, Howard would ask, ‘What is it that you wish me to see?’ His aim was to stimulate the student to make a critical examination of the design intent, and this disarm- ingly simple question opens up the range of design issues. It implies that, in any situation, the lighting designer has options to cause some things to be noticed more than others. In order to direct people’s attention purposefully, the designer establishes the concept of a visual hierarchy that is responsive to the overall design intent. For this to happen, the designer must be able to visualize the situa- tion. The design concept has to develop as a clear and detailed image in the designer’s mind. It should become a three-dimensional entity in which the designer is able to undergo the visual experience of the space, and above all, to see the lighting clearly.

Unifying design concepts

As the design concept develops in the designer’s mind as an increasingly detailed perception, there is a danger that the design

intent will be killed by complexity. As each object is envisaged with its desirable attributes brilliantly revealed, so it becomes easy to lose sight of the overriding concepts that give unity to the overall design concept. As we saw in Section 4.1, it was the notion of a coherent light field that brought Degas’ dancers into a single composition. A distribution of light and shade that may be complex and varied in detail may become an instantly recognized and unified light field through having the characteristic of coherence. This occurs naturally in daylit interiors, and is the basis of the love affair that many architects express for the ever-changing flow of light that characterizes these spaces. However, it is not necessarily restricted to daylit spaces.

It is always instructive to envisage the daytime appearance of a space before starting to think about the electric lighting, which involves applying the observation-based experience described in Part One. Perhaps the daytime appearance needs the addition of electric lighting to reinforce a visual hierarchy, but is this to complement the daytime light field, or to overturn it? Is the daylight to retain its coher- ence with the electric lighting altering the balance of the lighting patterns on selected objects, or is the electric lighting to change the perceived flow of light within the space? How do these notions of lighting relate to the changes of appearance as daylight fades and electric lighting becomes the dominant force? The skill to envisage lighting three-dimensionally is crucial. Particularly in situations where the design intent would be supported by allusory references and preserving the visual constancies, the lighting concepts described in Section 4.3 become the guides by which lighting designers can express a clear sense of design purpose.

User expectations

It is reasonable to assume that every person arriving at the design site has a reason for being there, and so each individual has certain expectations. There will be differences of expectations between those people for whom the space is familiar and those who are seeing it for the first time, and those who are coming to the space out of choice and those for whom it is a duty. These differing expectations are not of equal importance. It is more important that the customers like the ambience of a restaurant than that the waiters find their tasks easy to perform. Not all customers are of equal importance. Some restaurants seek to attract passing trade, while others depend upon maintaining a regular clientele. The former might place emphasis on the appearance of the restaurant seen from outside, while the latter may deliberately close off the view from outside.

The initial level of decision-making concerns: Whose responses matter? Why are they in the space? What are their expectations? The first stage of design development occurs when the mental concept develops from being perceived as a location to becoming a space that is seen through the eyes of a particular person. We will refer to this person as the viewer, and it is the expectations of this person that determine what are the relevant lighting crite- ria, and how these combine to form the design concept.

Lighting design strategies

From the preceding two sections, the special skill of the lighting designer is the ability to envision the design situation in light, and this involves the ability to ‘see the lighting clearly’. Is the experi- ence to be allusory or illusory? Where the aim is perceptual reassurance, allusory clues will dominate and the visual constan- cies will be supported. Where the aim is to attract attention, illusory clues may be presented within an allusory setting, such as by merchandise cabinets within a hotel foyer. The lighting in the cabinets can be arranged to give emphasis to selected object characteristics, and the effect becomes illusory, particularly when the source of light is concealed. Where the aim is to achieve an enhanced appearance, the illusory clues must dominate to achieve visual constancy breakdowns. The perceptual process is very adept at making sense of ambiguous information. These initial decisions are major determinants of the overall strategy for the lighting.

Consider how these concepts relate to interior lighting design. Typically, most of the elements that comprise a room and its contents are perceived in surface mode and have many differences of attrib- utes including differences of lightness. Materials such as glass or transparent plastic are perceptually more complex, as they may have some attributes that are perceived in surface mode and some which are perceived in volume mode. To provide for confident, unambigu- ous perceptions of surroundings these differences must be revealed, and for this purpose the lighting designer introduces luminaires which, generally, are perceived in illuminant mode and have the attribute of brightness. The illumination that they provide gives an overall impression of brightness, and also may impart patterns of light and shade that are perceived in illumination mode.

The role of constancy

The situation described in the previous paragraph is one for which visual constancy holds. Lynes (1994) has identified the following precepts which act to maintain constancy:

• adequate light • no disability glare

• high chroma, particularly on dimly lit surfaces • a variety of colours

• small white surfaces (‘separators’)

• natural organic materials with characteristic colours and textures • no large glossy areas

• sources of light should be obvious (but not necessarily visible) • recognizable texture

• good colour rendering.

There are some good reasons why lighting designers should aim to maintain visual constancy. As explained in Section 1.1, the process of perception is a process of trying to make sense of an incessant flow of continually changing data, where usually the aim is to enable one to orientate and find one’s way in a world of mostly stable objects. To this end, the process is attuned to filter- ing out effects of lighting patterns in order to construct a percep- tion of spaces and objects whose physical characteristics are recognized and clearly identified, and which together comprise a perceived world of stable spatial relationships. The design of, for example, an airport departure lounge should support users’ under- standable wish to orientate, find their way, and to feel reassured of the stability of their environment.

However, a world of perfect visual constancy would be a plain vanilla world. There are times when people choose to challenge notions of a stable reality. Some ride roller coasters and some seek out night clubs with strobe lights and other disorienting devices, but it is not necessary to go to such extremes to challenge visual constancy. When a designer determines a hierarchy of elements in the field of view and selects some of these to be enhanced, the implicit aim is to cause some loss of constancy. Constancy is not an all or nothing phenomenon, and whenever designers work to bring out the sheen of a material, or even to ‘reveal its natural colour’, they are modifying the perception of that material. To do this, they act against the precepts listed by Lynes. The light sources are concealed; sharp highlights and contrasts are provided; and often the selected object is separated from its surroundings by a frame or by low-reflectance materials. When a person cannot judge illuminance, their assessment of lightness ceases to be related to reflectance. Such viewing conditions enable designers to make objects ‘stand out’ and to make colours ‘glow’. These are situations in which illumination is being perceived in an object mode.

Returning to Brandston’s question, what is it that you wish the viewer to see? The lighting designer who learns to apply

observation-based experience to visualizing the design concept can be said to have got the picture.