Portrait of a Gentleman

The sitter of this portrait is possibly Caspar Calthoff (d. 1664).

In his ‘Inleyding tot de hooge schoole der schilderkonst’ (Introduction to the Art of Painting, 1678), van Hoogstraten discusses the optical theories of contemporary thinkers like Descartes, Bacon and Dighy, and adds his own comments. The scientists with whom he was in touch had a particular interest in optics, most notable was the Dordrecht mechanic and opticist Caspar Calthoff, whose portrait van Hoogstraten painted in 1650. Calthoff worked with important physicists like Christiaan Huygens, when he and his brother Constantijn decided to make their own lenses for their microscopes, it was Calthoff who supplied the grinding discs.