If you worked in either Renaissance or many famous contemporary artist studios you would find yourself collaborating on paintings. Collaboration is more common now than ever yet, it is widely unacknowledged in contemporary art because of concerns of diluting the brand name of celebrated artists. Much of the public today presumes that works by leading contemporary artists are executed in their own hand. This is not true. But, neither has this been completely historically true. For example, Verrochio’s workshop ( where young Leonardo da Vinci was apprenticed ) often employed many artists to work on the same image. In the example here at least three artists worked on the same painting. The nuanced distance was probably painted by da Vinci as was one of the angels. Botticelli probably painted another of the angels. The figure work was mixed. I sense da Vinci’s close observation in the depiction of translucent water perhaps, the first such example of artists rendering a body of water with translucence and movement. In the other example of collaboration, the painting from inside a moving subway car is a the joint effort of my son, Max Dunlop ( a professional artist lliving in NYC) and me. We each brough our own skills and imagination to the image. Max likes urban grit and he put the slimy smears on the window as well as many other contributions including providing the root image, a view out a lurching subway window.