We call the decrease in ink density towards the tail of the sheet "ink fall off." The ink form rollers are fully charged with ink while in the plate gap; if the image on the plate removes ink faster than the distributor rollers can replace it, the solid ink density drops towards the tail of the sheet. Some degree of ink fall off is normal. The amount of ink fall off is in some regards an indication of the efficiency of the inking system. The more ink form rollers a press has, usually the less ink fall off. To minimize ink fall off, the ink roller settings (especially ink forms to distributors) must be well-maintained. Good ink water balance will help print a darker solid ink density. Some press designs allow for the timing of the ink ductor to be changed, so the charge of fresh ink can be deposited on the plate at a specific time to re-ink the rollers and keep the density more even around the cylinder. This timing is often set to deliver the ink charge at the middle or tail of the plate to even the ink density around the cylinder. Mechanical ghosting is another phenomenon caused by ink being removed in one zone faster than it can be replaced by the distributor rollers.