Often it is necessary or desirable to balance the light intensity in one part of a scene with another this is especially true in situations where you dont have total light control as in bright contrasty landscapes sometimes it is also desireable to add colour to part of the photograph for example to add blue to only the sky lee grad colour filters are part clear and part colour they are available in grades of 1 through 5 with 5 having the darkest colour lee graduated colour filters are