Database: cre_Drama_Workshop_Groups
Question: Give me the description of the service type that offers not only the photo product but also the film product.
SQL: 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'