How many movies have Joe May and Mia May collaborated on?

They have worked on 30 movies together! Their first movie together was In der Tiefe des Schachtes (1912) while their highest rated movie together was The Mistress of the World, Part VIII: The Revenge of Maud Fergusson (1920). They have not worked together since Love Letters of Baroness S (1924). They are most known for their drama films together.