Well you can just get the position of the camera and determine the distance to the figure. You could place a small prop, like a ball at where you want the camera to focus. Write down the ball's position (xb,yb,zb). Then hit 3 or select the camera and note down the camera's position (xc,yc,zc). The distance is then Sqrt(xbxc+ybyc+zb*zc). That should be the focal distance to your prop ball.