LAUSR

I received my copy of this book to review at the same time that Tom Cornsweet’s death was announced. So, before I had the chance to open the book, I had read a dozen or so eulogies on social media, praising the man’s intelligence, wit and didactic skill. None of this surprised me, as Cornsweet’s previous textbook, Visual Perception, was well known to me — a marvellous book that had fi rst fascinated and enthused me and was, in no small part, a stimulus to pursuing a career studying visual perception more than 40 years ago. So, what of the new book, Seeing? First, Seeing is no more about seeing than Visual Perception was about visual perception. But that’s not the point. This is a book that stops and questions every step of what happens when light meets the eye, explaining in detail the underlying physics of the situation. The subject matter of most of this book is skimmed over in a page or two of most textbooks on vision. Cornsweet assumes a minimum of knowledge; he tells us that 10–12 means “ten with 11 zeros in front of it”. He devotes several pages to describing waves in water: how the distance from the peak of one wave to another is called ‘wavelength’, etc. These are things usually skated over in a textbook on vision, but this attention to the basics leads on to a real appreciation of what’s happening in the early stages of vision. And it’s full of real insights. For example, consider the standard diagram of the electromagnetic spectrum, from gamma rays, through visible light, to radio waves — a diagram in every book on vision I’ve ever seen, including this one. But Cornsweet makes one telling comment about it: if we were to represent the range between AM radio and X-ray wavelengths as the distance from New York to Los Angeles, then what distance would occupy the range of the visible spectrum? The answer is “an eighth Book review