I am easily able to get a shallow depth of field when I am close to my subject. However, when I am farther away, I cannot seem to get a shallow DOF. Let's say you have someone standing in the middle of a field and you want to get a shot of their entire body, but want the background blurred? I can't manage to capture that. I'm thinking it may be my lens?
I have a Canon Rebel Xsi with a 18-55 mm lens if that helps.