Early Ear Error
I attached myself to a guided tour of the National Gallery of Ireland the other week and learned that even the masters made mistakes. Judas, who can be seen kissing Jesus in the composition, had his ear lowered. You can see the vague outline of the earlier version about 3/4" above the existing one. This seems at odds with Hockney's assertion that Caravaggio [amongst many others] relied on the camera obscura; unless the model he used was possessed of very high ears, of course.