There’s a wonderful article about Weimar Republic painters in the new edition of The New Review of Books, which, alas, is not available online, so you’ll have to buy the magazine. The article discusses in quite a bit of depth several of the painters of that era - plus the background of the Weimer Republic, and it’s of particular interest for anyone who admires August Sander’s work. If you compare the paintings with Sander’s photos, on the surface there are no similarities whatsoever.