SRS, by the grain focuser not being of much use for edge sharpness, are you referring to checking at the borders of the print area? If so, you are correct that most of the magnifying focusers are not good in these areas. The Bestwell Magna Sight will give an accurate focus at the borders. I have found this to be very useful with negatives that are dark in the center with lighter, easily focused features nearer the edges. Also helps with alignment issues or using lens stage and easel tilt for perspective compensation.