During his career with the AP, Duncan has covered major league baseball, NFL football and NBA basketball as part of his regular duties in Cleveland along with news and enterprise assignments. National and international assignments include the 1984 and 1988 Republican National Conventions, the 1996 Democratic National Convention, the Persian Gulf “Tanker war” in 1987, Operation Provide Comfort in Somalia in 1993, the 1988 and 2006 Winter Olympics and the 1988, 1992, 2000, 2004 and 2012 Summer Olympics. Other major sports assignments include major league baseball playoffs and World Series and All Star games; 14 Super Bowls as photographer or editor; NBA Finals; the 1982, 1987 PGA championships and 1979, 1984, 1988, 1994 and 2004 US Open Championships.

Awards include two from the AP Managing Editors Association, four from the AP Sports Editors Association including the 1999 Thomas V. DiLustro award as sports photographer of the year and others from the Pro Football Hall of Fame and Baseball Hall of Fame contests. A former president and board chairman of the Ohio News Photographers Association, he received the Robert S. Carson Memorial Award from the ONPA in 2000.

Duncan has been married to the former Theresa McCarren since 1974. They have two sons: Matthew and Ian.