What's inside a digital camera? This is a cutaway view of the Canon Digital Rebel 1000D. Here's a more instructive diagram, showing the main optical paths. We'll take apart a camera in class. Most photography books talk about depth of field and depth of focus, but few of them give a formula for it. Here it is. N is the F-number, f is focal length, C is pixel size, and U is distance to the scene. W