Nelca Roco 

12.3.4 Light source colour properties

The colour appearance of the light used in a shop will contribute to the message the lighting
sends to would-be shoppers. A cool light appearance tends to convey a business-like
atmosphere while a warm colour appearance indicates a homely feel. As a general rule, the
colour appearance of the light sources used changes from cool to warm as the shop profile
moves from low budget to exclusive. Where daylight is used in the shop it is necessary to
choose a light source colour appearance that blends well with it. For some merchandise, the
colour appearance of the light used is important. Chiller cabinets look fresher and white goods
look crisper and cleaner under a cool light source. Conversely, gold looks more attractive when
illuminated by a warm light source.

The other aspect of light source colour properties that needs attention is colour rendering.
In general, light sources with a CIE general colour rendering index greater than 80 should be
used in retail premises.

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This will often be satisfactory but where the merchandise is most likely to be seen under
different lighting, e.g. a coat is most likely to be seen under daylight, it is wise to use lighting
that does not distort the colour of the merchandise relative to how the merchandise will be seen
in use. For some retailers, there can be a temptation to choose a light source that enhances the
appearance of the merchandise. An example is the notorious butcher’s lamp, a lamp that
exaggerates the redness of meat. This is a temptation that should be resisted. In other shops it
will be important to choose a light source with colour rendering properties that give an
appealing appearance to human skin, particularly in areas where an individual’s appearance may
be closely examined, e.g. fitting rooms. While the CIE general colour rendering index is a
useful guide, the final choice of light source is best made by viewing the lit objects of interest.

12.4 Approaches to retail lighting

12.4.1 General lighting

General lighting in shops with a low budget or value for money profile is usually provided from
a regular array of luminaires (Figure 12.1). These luminaires range from bare fluorescent lamp
battens through recessed fluorescent louvres to pendant metal halide globes. The purpose of
such general lighting is to produce a uniform illuminance over the relevant plane without
causing glare.

In shops with quality or exclusive profiles, the architecture is more likely to be a feature of the
store and the general lighting will need to be integrated with it. This may involve the use of
recessed downlights, cove lighting or suspended uplights rather than a regular array (Figure
12.2). Regardless of the lighting approach used, the appearance of the luminaires needs to be
consistent with the style of the shop.

12.4.2 Accent lighting

Accent lighting is designed to provide additional illuminance on some areas so as to emphasise
specific items of merchandise and to provide a meaningful variation in brightness and shadow
throughout the store. If well done, accent lighting can guide shoppers through the shop and
draw their attention to merchandise. The best form of accent lighting depends on the area
to be accented.

For large area wall displays, wall washing luminaires fitted with fluorescent lamps are used
(Figure 12.3). For gondola displays, the lighting can be built into the gondolas (Figure 12.4).
For small area accent lighting, aimable spotlights attached to power track should be used (Figure
12.5). Whatever the form of accent lighting, some flexibility is required. This is because the
nature and aiming of accent lighting will depend on the merchandise to be accented. As the nature and layout of the merchandise changes, the accent lighting will need to change.

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Where wall washing luminaires are used, the important characteristic of the luminaires is the
light distribution, the ideal being a uniform illuminance from the top to the bottom of the wall.
A similar consideration applies to accent lighting built into gondolas. The illuminance
distribution from the top to the bottom of the gondola should be as even as possible. Where
spotlights are used, the luminous intensity at the centre of the beam, the shape and dimensions
of the resulting light spot with respect to the size and shape of the area to be lit are important.
Accent lighting in shop windows has competition from daylight reflected from the window
glass and from the windows of nearby shops. Depending on the shielding from daylight and the
lighting of adjacent shops, the general lighting of the window during the day needs to be in the
range 500 to 2000 lx, while accent lighting needs to be in the range 3000 to 10,000 lx. These
illuminances should be reduced after dark.

12.4.3 Display lighting

The function of display lighting in shop windows is to gain the attention of passersby and to
make the merchandise look attractive. Inside the shop, the main purpose of display lighting is to
emphasise the desirable features of specific merchandise. Inside the store, display lighting can
be applied to merchandise open to examination (Figure 12.6) or to merchandise in showcases.

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Display lighting is designed to gain attention by using an appropriate combination of brightness,
colour and modelling. Relative brightness can be expressed in terms of the luminance ratios
given in Table 12.2. The higher is the luminance ratio, the more likely the display is to gain
attention. As for colour, strongly coloured light on an object of the same colour will deepen the
colour whilst strongly coloured light on the background and surroundings will change the
atmosphere. The modelling achieved depends on the relative strength of light delivered from
different directions. Modelling is usually achieved by some combination of key-light, fill-light,
back-light and up-light. Table 12.3 describes these techniques.

Table 12.3 Descriptions of the components of display lighting

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