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'