I have a question about DEPTH OF FIELD. I'm using 8x10 with 240mm lens. Is it possible to calculate the NEAR LIMIT where I can get focus when I shoot something with infinity at f/45. In another words, I like to know the distance from nearest point where I can focus to infinity at f/45 with my 240mm lens. For example, at f/45 I can get focus from 20 meter to infinity.