Shunga were produced between the sixteenth century and the nineteenth century by ukiyo-e artists, since they sold more easily and at a higher price than their ordinary work. Shunga prints were produced and sold either as single sheets or—more frequently—in book form, called "enpon". These customarily contained twelve images, a tradition with its roots in Chinese shunkyu higa. Shunga was also produced in hand scroll format, called kakemono-e (掛け物絵). This format was also popular, though more expensive as the scrolls had to be individually painted.