This book is an exploration and appreciation of cameras and their optics, covering all major lens types from the earliest to the most recent--including those roving the surface of Mars. A recurrent theme of this book is that lens types invented in the 19th century are just as useful in the 21st century. Another continuing theme is the impact of the digital revolution and the use of imaging in radically new circumstances. This book should be of interest to any who are curious and want to know more about the glass on the front of their cameras.