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L ight is a fascinating phenomenon that influences our perception and health. Natural light is particu-
larly diverse and has shaped our light requirements over the course of evolution. As lighting desi-
gners, we learn from nature and take cultural backgrounds into account. In living spaces, we compose
light to create variety, openness, cosiness and joie de vivre – light creates atmosphere and magic. Besides
visual and psychological effects, light also has biological effects on our health. Healthy living means
bringing plenty of daylight into our homes and supplementing it sensibly with artificial light. Sustainable
lighting involves respecting darkness and taking into account the dynamics of day and night.

Development of light preferences in different cultures

Cultural diversity in the use of light is reflected in different lifestyles, architecture and urban development
projects. This diversity leads to different likes and dislikes, particularly with regard to warm or cold light, Grafik: Ulrike Brandi Licht
depending on the latitude of the location. The duration of the twilight phases characterises people’s vie-
wing habits: people near the equator are familiar with a quick transition to bright artificial light, as the
change from bright daylight to dark night only takes a few minutes. Near the poles, twilight lasts longer, Mindmap Lichtcharakteristika • Mind map of lighting characteristics
with a long period of warm orange evening sky, so people in the north prefer warm artificial light in
their homes. Understanding the psychological effects of light on people helps us plan light appropriately
and strengthen certain uses intentionally. Darker lighting situations appeal to the imaginative, emotional
side of the brain, while brighter rooms appeal more to the rational side. Psychologist Ingrid Gehl has
developed a system that addresses the psychological basic needs of people regarding architecture and
urban planning. There are eight elements of psychological well-being: social interaction, privacy, space
for diverse experiences, endowment with meaning, play, structure and orientation, personal control, and
aesthetics and beauty. Differentiated light is the secret to good lighting design. Lighting solutions in our
homes reflects our personality and style. Smart control technology allows us to play with variations in
light colour and brightness, providing room for creativity. However, the healthiest light is natural day-
light. With its day-night rhythm, it influences all living beings on Earth and controls important biological
processes. Particularly noticeable are the psychological effects of light deficiency during seasonal chan-
ges. Spending time outdoors is the best protection against many physical and psychological illnesses. It’s Grafik: Ulrike Brandi Licht
important to receive all wavelengths of daylight as well as sufficient darkness for sleep. To achieve a high
light dose in the morning, artificial light can be supplemented on cloudy days with daylight lamps and
“light showers”, which medical research shows can help with depression and fatigue. When we inte- Mindmap Lichtstimmungen • Mind map of lighting moods
grate smart lighting control, we can also tailor it to our daily rhythm. Healthy light considers the times
of day and corresponds to the human circadian rhythm. Artificial light is based on the characteristics
and moods of natural light, and lighting scenes follow the course of the day. A dynamic change between
lighting scenes, from morning to night, supports the stabilisation of our circadian rhythm. For us lighting
designers, natural light is the starting point and benchmark: if architects, urban planners, and clients
take these insights into account early in their considerations, we can integrate daylight into buildings.

Dialogue between materiality and light

Light and surfaces engage in a constant dialogue: without light, there is no space, and without surfaces, Royal Academy of Music, London; ritchie*studio; Foto: Adam Scott
light remains invisible. Understanding this mutual dependency is crucial. Within a light fixture, light and
surfaces interact, whether it’s the glossy reflector directing light beams or the transparent lampshade
diffusing light broadly. These correspond to two fundamentally different light characteristics found in
nature: sunlight and skylight. The reflector enhances direct, brilliant light, while backlit surfaces produce
shadowless, even light. Human perception, shaped by interpretation and experience, plays a significant
role. Pleasant lighting often combines both types, as diffuse light alone can feel lifeless and boring, while Brillantes Licht trifft auf weich reflektierendes Holz • Brilliant light meets softly reflecting wood
direct light alone may be too dramatic and glaring. Natural daylight offers a vast range, up to 100,000
lux, but indoor spaces typically range from 50 to 500 lux. Fortunately, we can adjust light intensity
and combine sources to suit different conditions and personal preferences. The colour temperature has
also become important. Measured in Kelvin, lower values indicate warmer light: candles emit light at
2200 Kelvin, incandescent bulbs at 2700 Kelvin, and LEDs for residential use typically range from 2700
to 4000 Kelvin. Colour temperature of white light, along with object colours, evokes associations and
shapes our perception of lighting ambiance. Additionally, the colour rendering index (CRI) is a crucial
quality criterion for luminants; it measures how accurately colours appear under a light source compared
to natural light. High CRI values ensure natural-looking colours. Combining various light sources with
different materials, colours and finishes yields different lighting moods. A practical experiment conduc-
ted at the AIT-ArchitekturSalon Hamburg demonstrated this phenomenon, showcasing how different Foto: Martina Orsaka für CIRECA Domaine de Boisbuchet
surfaces react to consistent lighting conditions. The experimental set-up included a white room and a
light source with 2700 Kelvin and Ra 98 in a constant position as well as changing materials (yellow
matt cardboard, the shiny golden side of a rescue sheet, solar control glass, blue matt cardboard). The
effect on the room can be seen on all surfaces. For example, a kitchen table made of cherry wood reflects
warmer light onto the faces of the people sitting there than a glass table or a steel-blue painted surface. Die Kerzenflamme: warme und bewegte Lichtquelle • Warm and moving light source

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