Caspar David Friedrich ( September 5 , 1774 â `` May 7 , 1840 ) was a 19th-century German Romantic landscape painter , generally considered the most important of the movement . Caspar David Friedrich ( September 5 , 1774 â `` May 7 , 1840 ) was a 19th-century German Romantic landscape painter , generally considered the most important German artist of his generation .