Light enables us to experience space. The distribution of light is vital for spatial experience but has not been the main focus of previous research on lighting. The lighting designer’s professional knowledge is to a great extent experience-based and tacit. With design practice as the point of departure, this thesis aims to explore spatiality and enclosure in relation to the distribution of light – with the intention of increasing subjects’ understanding of what can be regarded as a space, and to show how spaces can be shaped by the distribution of light. By focusing on users’ experiences and interpretations, relationships between the distribution of light and perceived spatial dimensions and experienced spatial atmosphere have been investigated. The main contribution of this thesis is to widen the base of knowledge that lighting designers, architects and customers can use as a common reference. This thesis is based on three studies: the Scale Model Study, the Auditorium Study and the Church Park Study. The thesis includes concept- and method development. The mixed methodologies comprise a range from introspective phenomenological observations to deep interviews and questionnaires. The experimental setups have also shifted from scale models to real-life interior and exterior settings. Consequently, a quantitative approach has complemented the mainly qualitative approach. Through artistically based research, patterns and relationships are dealt with in complex real spaces. The findings of these studies lead to a discussion of when, why and how patterns of brightness and darkness influence spatial perceptions of dimensions. The findings also show that brightness not only contributes to our experiencing a space as more spacious than it really is, but in certain situations brightness can actually have the reverse effect. Furthermore, darkness can contribute to a spacious impression, which has hardly been discussed in previous research. What subjects regard as a space may shift between the clearly defined physical space and the perceived space, which include light zones. Light zones can create a sense of inclusion or exclusion for subjects, which affects their sense of community and their feeling of safety. Light topography, e.g. the height of luminaire positions, as well as light direction influence the way we experience the private and the public. Enclosure can, if related to visible spatial boundaries, facilitate reassurance and safety.