Until recently, the phenomenon of copying in medieval book painting has been considered mainly in terms of the reconstruction of pictorial sources used for the composition or iconography of miniatures, initials, or decorative elements. Although historic sources only rarely mention the circumstances of manuscripts' production, one particular widely-accepted hypothesis has prevailed until now, according to which artists used model drawings or sketch books with the aim of facilitating the production of copies and the creation of new picture cycles. However, it is no longer sufficient to regard...