An ever-increasing array of design visualisation tools are available to designers. As such, design education is constantly challenged to keep up with these trends so that students are best equipped for entering industrial practice. This paper reports a study into the use of digital sketching, a relatively new digital visualisation tool. The study aims to identify thematic differences in how students and practitioners perceive digital sketching. These are given in terms of the tool's characteristics, and how these characteristics guide its application in early stages of the design process. Data on perceptions is captured using design diaries and semistructured interviews. Results show key differences in the way that practitioners perceive the intent of visualisation. Practitioners focus on iterating towards a solution during the design process. Students are much more focused on the task of creating visualisations. This reveals an underlying contradiction in the way tools are perceived between creating visualisations to gain expertise or skill, versus creating them to advance the design process. The insights help improve our understanding of how the different characteristics of digital sketching inform its use. We reflect on how we educate students with respect to selecting and using digital sketching. We conclude with implications for education of digital sketching, as well as other emerging digital visualisation tools.