The question behind Calculation is whether the age of film photography has truly ended - cameras, film stock and dedicated shops still exist, and plenty of young photographers keep using it. The book is Igor Mukhin's answer to a question that occurred to him after his exhibition Accomplices: whether portraits made over many years, for many different reasons - private histories, chance encounters, commissioned sittings - could be united into a single statement, and on what basis they might be selected. Faced with endless contact sheets, he noticed the frame numbers themselves, and built the book's method around them: a selection drawn strictly from archival contact sheets of Kodak film, each keyed to its own frame number, so that older Soviet, East German and other stocks - without that consistent numbering - fell outside the project, and some frame numbers turned out to hold a surprising concentration of successful portraits while others yielded almost nothing.