I felt like being a “geek” lately. Hence, I wrote a static page on depth of field (click here to go there). It is quite technical, and even some mathematics is used! Don’t be afraid though: I have added some explanatory drawings, which might help you understand.
This page is part of the “Advanced knowledge” section, so it is slightly more complex than my other pages. Good luck reading, and feel free to ask any questions, or leave comments for improvement!