Jan Van Eyck, Rollin Madonna, 1439 (left)
Rembrandt, Night Watch 1642 (right)
Heinrich Wolfflin was a 19th Century art historian whose work on the styles of Renaissance and Baroque painters uncovered tendencies which help us to make sense of the style and composition of a wide variety of paintings, both from these eras and from others. His approach is to define by way of comparison and contrast a handful of compositional devices which help us to make better visual sense of the works.
Of the two pictures above, the Van Eyck is from the Renaissance and the Rembrandt from the Baroque period. Can you see how to make sense of Wolfflin's categories with them?
Multiplicity and unity form the pair of terms which is most obviously relative, for all great works are unified in one way or another. What Wolfflin means here is that the Renaissance painting is made up of distinct parts, each one sculpturally rounded in its own right, each one clearly filled with its own single, local colour, while the unity 0of the Baroque picture is much more thoroughgoing, largely achieved by means of the strong, directed light. In [Rubens' Holy Family with St. Frances] all the units - and there are very many of them - are welded into a single whole: none of them could be isolated. Colours blend and mingle, and their appearance depends largely on how the light strikes them. For instance, the Madonna's red dress looks truly red only in parts, other parts being darkened to grey in shadow, something which is much less true of the cloak of the saint to the far right in Raphael's painting, [Madonna and Child Enthroned with Saints]. The even, diffused light in the Renaissance picture helps to isolate elements so that a multiplicity of independent units can be balanced against one another. (Woodford, Looking at Pictures, 92-3)