Near the end of Imber’s Left Hand, the 2014 film about artist Jon Imber’s struggle to keep on painting as he was dying from ALS, there is a beautiful scene of a show of the hundreds of portraits that Jon painted, in the last year of his life, of friends in Boston and Maine who came by to keep him company and to help. Some of those friends, and others who had never met Jon, gathered together, teary-eyed, at 13FOREST Gallery after watching the Arlington International Film Festival’s screening of the film.