Interesting Little Tool

[Gdad]

An online Depth of Field Calculator- just enter the camera and lens info and you can easily see how aperature effects the depth of field.

http://www.dofmaster.com/dofjs.html

[MarkBarbieri]

This page has several good calculators. I especially like the dimensional field of view calculator. It is useful when someone wants to know if a zoom is going to be "long enough."

http://www.tawbaware.com/maxlyons/calc.htm