The thesis emerged from two streams. First, from an interest in portraiture. Both the portrait as an art object and portraiture as a social process are mediated by power relations, yet, despite this, it is a genre that has been relatively underexplored by sociology. Second, as a response to calls within the sociology of art for approaches that, rather than maintaining a distance, seek to take the artwork “seriously” as a source of “social knowledge that is of its own worth” (Harrington, 2004, p.3). Explorations of the ‘affordances’ that material objects provoke in socially situated subjects reflect this interest in capturing the ‘in-itself-ness’ of the art object in ways which are “congruent with social constructionism” (De la Fuente, 2007). These two streams inform the thesis’ three aims, addressed through three case studies of five 20th Century portraits. First, to present portraiture and its relations of power to the sociological gaze. Second, to develop an empirical approach, characterised as ‘taking a line for a walk’, that seeks to keep in play: the material properties of the image and what these may afford to a situated viewer; to explore how these affordances operate to constitute the subjectivities of the individuals portrayed and the artists; and to consider how these processes play out in and through the processes of consecration of the object and artist within the cultural field. Third, to make a contribution to understanding how to capture sociologically the ‘in-itself-ness’ of the art object. The thesis suggests the value of an approach that keeps in focus the art object and the context of its circulation, helping to deepen understanding of the operation of the field. Second, it reveals portraiture as an exercise of power, including in the constitution of the subjectivities represented in and through the portrait. Third, it suggests the continued difficulties of empirically capturing the ‘in-itself-ness’ of the art object.