On the occasion of the exhibition by artists Filipa César and Louis Henderson, Op-Film: An Archaeology of Optics, at Espace Khiasma (29th March — 28th April in Les Lilas, on the outskirts of Paris), Khiasma presents Black Lens, a two-day experimental seminar at La Colonie (Paris) on 29th-30th March, associating a series of screenings, audiovisual performances and conversations by artists and theorists from France, Germany, the UK and Portugal.