On an evening late in the season at Wrigley Field, a narrow beam of low sunlight reached the top step of the Chicago Cubs’ dugout. Pete Crow-Armstrong, the front-runner for National League MVP, was standing on that step, a spot he usually leaves to the team’s veterans, as the take-the-field video played. Team photographer Matt Dirksen saw the light land behind him. He had a few seconds to get the picture.