This article discusses the use of video cameras in participant observation drawing on approximately 300 hours of video data from an ethnographic study of Swedish family life. Departing from Karen Barad's post-humanistic perspective on scientific practices, the aim is to critically analyse how researchers, research participants and technology produce and negotiate children's corporeal privacy. Ethnographic videotaping is understood as a material-discursive practice that creates and sustains boundaries between private and public, where videotaping is ideologically connected to a public sphere that may at times 'intrude' on children's corporeal privacy. The limits of corporeal privacy are never fixed, but open for negotiation; ethnographers may therefore unintentionally transgress the boundary and thus be faced with ethical dilemmas. The fluidity of privacy calls for ethical reflexivity before, during and after fieldwork, and researchers must be sensitive to when ethical issues are at hand and how to deal with them.