Rogier van der Weyden
On the strength of the reputation of his collection, Renders profiled himself as an informed connoisseur of Flemish old masters. He published studies in which he cast doubt on the existence of Hubert van Eyck and identified the Master of Flémalle with Rogier van der Weyden (current scholarship identifies the Master of Flémalle with Robert Campin, the teacher of Rogier van der Weyden). These publications aroused lively polemics with reputed art historians.