text: Besides the works of the 14th-century masters Duccio , Pietro , and Ambrogio Lorenzetti , as well as Simone Martini , see Siena 's 16th-century Mannerists , painting at a time when the Renaissance teetered on the brink of effete Beccafei 's dreamy Birth of Mary and a highly decorative Christ at the Column by Sodoma .
  
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  The 16th century was a turbulent yet transformative time in Renaissance art .