Many folks have erroneous beliefs which they "know" to be true, but are actually very, very false. This is one of them. A quick check of the DOF indication about the same distance on two of your own lenses would have confirmed your error before pressing send on your post. So that all can see that DOF is dependent on the focal length of the lens as I said, I will provide my example from: http://www.silverlight.co.uk/resources/dof_calc.html 100mm lens at f/4 set at 10 meters... Total DOF = 2.659 meters. 300mm lens at f/4 set at 10 meters... Total DOF = 0.285 meters. Now, you may be tempted to say that this is only apparent because the 100mm photo must be blown up by a factor of three to provide the same cropped scene. Consider that 0.285 x 3 = .755, not 2.659. Regards, Bob... From: "Ken Sinclair" <photo1@telusplanet.net> > Bob, > > I would be more tempted to use the phrase "apparent depth of field", since > any two (or more lenses) set on the same camera, sitting on a stationary > object (such as a tripod) and set at the same f-stop, focussed at the same > distance, will have the same depth of field. > > It is just the apparent DOF will be greater as the focal length decreases > > Ken, > > >Another reason for changing focal length is to control depth of field (DOF).
