The remainder of the 1660s, especially up to 1668, produced most of his best works, which increased in size and complexity as he perfected his style. His landscapes are sunnier than the equivalent scenes by Jacob van Ruysdael, with the principal trees typically seen with sky behind. His skill at varying effects of light and colour throughout a work is exceptional. He often makes use of double vanishing points to add interest to the composition. Some of his compositions, as late as 1664, are near-copies of Jacob van Ruysdael, and he often repeats his own compositions with variations; four of the five works in the Wallace Collection have other versions. For some of these he made use of assistants, though little is known about them or their role.