How much space in front of the lens will be in focus? That question defines Depth of Field - but this simple concept has lead to a staggering amount of confusion in today's multi-format camera environment. Through some fundamental scientific demonstrations, we will clarify concepts like circle of confusion and lens equivalency. For fundamentals make sure you check out: The History and Science of Lenses ****** The Properties of Camera Lenses ****** *ERRATA* The ISO ISO in regards to Lens Equivalents should be multiplied by ISO^2 because we're dealing with two dimensions not just one. Multiplying by just the ISO will result in slightly darker image (as see in the demo) Some people have jumped to the conclusion that the Circle of Confusion is the Pixel Size. The CoC is LIMITED by the Pixel Size in that it cannot be smaller than the pixel size, but in most cameras the pixel size is much smaller than the CoC (or at least by a standard CoC that calculators use for determining depth of field). This explains why a Full Frame 12MP camera will have the same DoF as a 50MP camera. But if you enlarge the photo enough, eventually you will be able to see more detail in the 50MP because it can resolve finer details. The reason why we use analogy of setting the pixel size to the CoC is it's an easy way to visualize the phenomenon and it's a common experience when jumping between standard definition and high definition video. But remember pixel size (pixel density or pixel pitch) is generally not a factor in depth of field - only how much you can enlarge an image.