The use of video recordings as a data source in qualitative research presents challenges when it comes to selecting time scales. Here, we discuss the implications of selecting time scales with regard to the interpretations and conclusions of a classroom event. The analysis draws on data from the PISA+ project, a large-scale video study of six ninth-grade math, science, and reading classrooms in Norway. Our data include video recordings of three lessons from one of the recorded classrooms. We examine how five 15-year-old students prepared for and performed an oral presentation. The first analysis, time scale 1, focuses exclusively on the students' oral presentations, while the second analysis, time scale 2, includes the students' oral presentations as well as their work during the preparation phase. We compared the results of the two analyses and found that the length of the video footage (the chosen time scale) impacted the findings of the study.