Wikipedia has some formulas, but they do not condense well to rules of thumb. That is probably why people carry tables with depth of field on them. I printed out 4 tables on 2 notecards with common focal lengths. My idea is to reference these, or study them while shooting in non-pressure situations until I just get more familiar with what focal length/aperture/subject distance give what kind of depth of field. I haven't spent much time on it and it will probably be difficult and take many years. I would think if someone like a wedding photographer who primarily shot with a 35mm and 85mm lens or something like that, might be able to almost memorize the depth of field characteristics for those two lenses, but for zooms.....?


http://en.wikipedia.org/wiki/Depth_of_field