Example 1: The visitors are guided to the building entrance by means of increasing illumination densities.

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1 On the basis of three examples, luminance values are compared with each other in specific applications. The examples are the square in front of a historical function building, a train station concourse and a shop for exclusive accessories in a pedestrian zone. In the description of the illumination, we shall proceed from the lowest luminance and define this as 1. All other values are calculated according to this, to illustrate the ratios between the luminance values. Example 1: The visitor is received on a generously dimensioned square, which one can reach through a small park. Vehicles may only stop briefly in the access road to pick up and drop off guests. The park is framed by unshielded bollards, whose light allows good face recognition on the footpath. At the same time, the pedestrians are clearly visible for the drivers. The square in front of the historical building is illuminated with light building elements. This gives the area a structure. A generously dimensioned staircase, where recessed wall luminaires are installed in the side walls, leads into the building. The entrance area welcomes the guest with an arcade with pillars illuminated with in-ground floodlights. Unshielded ceiling luminaires are used within this covered area. On the roof of the arcades, surface washers emphasise the upper areas of the building façade. In the direction of the entrance, the level of illumination increases more and more. Beginning with the lowest luminance with the bollards at the edge of the park, the level rises to 1 : 2 towards the road, continuing on the square to 1 : 2 : 3 and towards the staircase to 1 : 2 : 3 : 5. Directly at the entrance, the 12-fold luminance level is reached compared to the starting position, that is 1 : 2 : 3 : 5 : 15. The visitors are guided to the building entrance by means of increasing illumination densities. 4 lx 8 lx 12 lx 20 lx 60 lx 36

2 1.05 Light planning Luminance in proportion Entrance Staircase Square area Access road Adjacent park The bird s eye view illustrates the relationships of the luminance values. The lowest luminance value (4 lx) is defined as 1. This means relationships of 1 : 2 : 3 : 5 :

3 50 lx 200 lx 300 lx 150 lx 200 lx Example 2: Two massive structures are connected with an arched roof. The front sides of this train station concourse are glazed, and provide a clear view as far as the platforms. On the right and on the left, business shops lead into the building. The information desk is in the centre of the hall. In the extension of the hall, at the back, stairs lead to the platforms. The luminance levels are considered from the entrance to the station to the stairs leading to the platforms. The lowest luminance is at the covered area directly in front of the station and is thus 1. As we enter the entrance hall, the luminance increases threefold. The open information desk in the centre is emphasised with additional light. This results in relationships of 1 : 3 : 6. The lighting in front of the business shops is slightly stronger than that of the station concourse. The illumination of the shop windows has not been taken into accounthere, since this may vary according to the time of day and is controlled individually by the respective shop owner. Compared to the entrance, the passages have a luminance of 1 : 4. The lighting towards the stairs leading to the platforms becomes somewhat darker again. Here, the luminance is twice as high as in the entrance area, that is, 1 : 2. 38

4 1.05 Light planning Luminance in proportion Passages to the platforms Information desk Shop passages Station concourse Entrance This view illustrates the relationships of the luminance values. Here too, the lowest luminance value (50 lx) is defined as 1. The resulting relationships are 1 : 4 : 6 : 4 : 3. 39

5 1000 lx 50 lx 200 lx 1800 lx 500 lx Example 3: The evaluation surface of the shop stretches from the pedestrian zone directly in front of the shop to the interior rear wall, where there is a backlit presentation of goods. In this situation too, we proceed from the lowest luminance value directly in front of the shop in the pedestrian zone. The entrance is flanked by two shop windows whose illumination is adjusted to the level of daylight using a light control unit. The figure measured at floor level is 200 lx. The 500 lx mark is reached at the cash desk. This means relationships of 1 : 4 : 10. The goods on the side walls are presented with 20 times the luminance compared with the entrance. Very high quality products are to be found in the facing wall in integrated and backlit display cabinets. In front of these there are small tables for sales conversations. Here a degree of illuminance of 1800 lx is required. Proceeding from the lowest luminance value, this results in a relationship of 1 : 36. In this way, the customers attention is drawn directly to the goods. The examples listed above show possible luminance distributions. From the darkest area to the brightest area, some of the differences are extreme. Accordingly, the light is felt to be pleasant. Why? In the function building (example 1), the entrance represents the brightest point. The luminance increases gradually for the visitors as they arrive. The entire situation can be grasped at a glance. These factors convey a feeling of safety. The spatial situation is clear, and is given a clear structure through light. The path towards the event is shown through the increase in luminance. Visitors can easily find their way around, and get the feeling that they are in good hands. In the station (example 2) soft transitions between the various luminance levels are important. Many travellers are in a hurry. The focus is on information about train connections. Highly contrasting lighting conditions would interfere. Here, a build-up of tension in the illumination has largely been dispensed with. Certain zones are emphasised slightly, by increasing the luminance values at the information desk and in the shop passages. All in all, the light in the station is uniform and conveys a feeling of visual tranquillity. The eye hardly has to adapt. The illumination in the exclusive shop (example 3), on the other hand, is tense and accentuated. High contrasts attract the attention directly to the presentation of the goods. Despite these differences in light intensity, customers find that the light is pleasant. Here too, the entire situation can be grasped quickly. Very strong light-dark contrasts appear within the human field of vision. Apparently these contrasts are added up to form an average value, for they do not cause the eyes to tire rapidly. If the eyes were exposed to such strong alternating contrasts, their adjustmentwork would be enormous. If an illumination situation can be grasped at a glance, therefore, sharp differences in luminance distribution can be used meaningfully. In this way, an arc of tension can be built up with light and persons can be guided and accompanied. If a room is uniformly illuminated with a certain luminance and the dimensions of this room completely fill the human field of vision, the transition to a more strongly or less strongly illuminated area should only be gradual. In this way, the eye has a good chance to adjust to the change in lighting conditions without becoming tired. Here, jumps between greatly differing luminance levels would lead to glare and rapid fatigue. Good illumination makes a significant contribution to our well-being and often leads to business success. In the end, the light designer must decide on site which light is the best in the situation in question. 40

6 1.05 Light planning Luminance in proportion Sales tables Shelves Counters Floor In the shop window, the luminance is subject to daylight-dependent control. Pedestrian zone In the shop, the relationships between the luminance levels vary greatly. Here too, the lowest luminance value (50 lx) is defined as 1. The resulting relationships are 1 : 4 : 10 : 20 :