A dramatic transformation took place in Italian art between the late medieval tradition, practised until about 1400, and the elegant sophisitication of the High Renaissance. Paintings in the earlier period invariably had religious subjects and were intended as an aid to Christian prayer and devotion. They were painted in the technique of egg tempera on wooden panels, usually with gold panels.
The innovations of the Renaissance were achieved through the closer study of nature and of classical antiquity, and the application of the rules of perspective. Artists experimented with oil paint and canvas supports, and broadened their range of subjects to include literary and mythological themes and portraits.
The two main themes of early Netherlandish and German painting were portraiture and religious subjects for public and private devotion. Royal or aristocratic rulers and the Church remained the principal patrons of this period, but wealthy citizens also increasingly commissioned paintings. Portraits were sometimes included in altarpieces, as in Hugo van der Goes's Trinity Panels. In northern and central Europe altarpieces usually consisted of a central image with attached wings or shuuters, which would have been opened on religious feast days.
The Reformation, which challenged traditional Catholic beliefs and practices, had a major impact on sixteenth-century northern art, introducing specifically Protestant imagery.