the digital sensor is smaller than film, so you are magnifying the image the lens produces more. So what is "acceptable" sharpness in film may not be acceptable anymore in digital. It's like judging the focus point and DOF of a print from 2m distance versus 0.5m distance.
The DOF scale in lenses is film based, so to use it with DB, you have to compensate the aperture, +1 stop at least. So if the scale shows you to use f/8, you leave the focus at that but dial f/11 for aperture.