I've been going through the fast.ai course, and pre-training is like witchcraft, it's so spookily effective. You can take a 15MB mobilenet model, add a layer a

I've been going through the fast.ai course, and pre-training is like witchcraft, it's so spookily effective. You can take a 15MB mobilenet model, add a layer at the end, fine tune with half a dozen examples of a few different image classes (in a few minutes on a consumer grade laptop), and recognize lots of different examples in real time with a web app reading continuously from a webcam. The advances made in Computer Vision in the last ten years are mind blowing.