By the late 1630s Rembrandt had produced a few paintings and many etchings of landscapes. Often these landscapes highlighted natural drama, featuring uprooted trees and ominous skies ("Cottages before a Stormy Sky", c. 1641; "The Three Trees", 1643). From 1640 his work became less exuberant and more sober in tone, possibly reflecting personal tragedy. Biblical scenes were now derived more often from the New Testament than the Old Testament, as had been the case before. In 1642 he painted "The Night Watch", the most substantial of the important group portrait commissions which he received in this period, and through which he sought to find solutions to compositional and narrative problems that had been attempted in previous works.