His early works, showing the influence of Tassi and of Dutch and Flemish artists, are busy, animated, and picturesque. They are full of charm and effects of surprise. His smaller pictures, painted on copper, reflect the spirit of the German artist Adam Elsheimer, who had died in Rome in 1610. A pattern common in the early paintings is a dark mass of foliage on one side in the foreground contrasted with a misty sunlit distance on the other. This is an idealized harbour scene flanked on one or both sides with palaces, the latter often being adapted from actual ancient or contemporary buildings.
Tall ships ride at anchor, recently arrived or preparing to depart.
Light, however, is the key feature of the seaport pictures. Its source is often a visible sun just above the horizon, which Claude first introduced in 1634 in Harbour Scene and, in so doing, used the sun as the means of illuminating a whole picture for the first time in art. Recession is further emphasized by subtle atmospheric perspective achieved through a gradual diminishing of the distinctness of outline and colour from the foreground to the background. The light is nearly always that of dawn or evening. Beginning around 1640 Claude began to make his compositions more classical and monumental.