What is the description of the service type which offers both the photo product and the film product?
select t1.service_type_description from ref_service_types as t1 join services as t2 on t1.service_type_code = t2.service_type_code where t2.product_name = 'photo' intersect select t1.service_type_description from ref_service_types as t1 join services as t2 on t1.service_type_code = t2.service_type_code where t2.product_name = 'film'