We conducted a study to explore the values and qualities of 'grassroots documentaries', framed around the production of two parallel documentary films with a London-based opera company. A team of professional filmmakers produced one film and the other was an exploratory form of grassroots documentary. We studied the different production activities through observations, interviews and a reflective workshop at the end of the study and evaluated the resulting films. Our analysis reveals critical insights that could inform the next generation of technological systems to support user-generated video content (UGVC) production, particularly in collaborative contexts such as grassroots communities.