The human eye can see well over a wide range of lighting conditions, but a machine vision system is not as capable. You must therefore carefully light the part being inspected so that the machine vision system can clearly 'see' them. You want lighting that 'amplifies' the elements of the part that you want to inspect and 'attenuates' elements that you don't want to inspect. Proper lighting makes inspection faster and more accurate. Poor lighting is a major cause of failure in machine vision inspection systems.