This is about the language of photography not merely style. Clearly these photographs were taken over several months. Hockney, along with others (Vaughn Grylls) posed the question whether it was sufficient to create a photograph from a single negative. Hockney ceased his major commitment to photography around 1986 and has frequently pointed out his perceived inadequacies of the photographic process. Others have carried on the enquiry. You can see around 40 related compositions at Gainsborough's House Museum until June 23rd