Graduated filters (or more simply ‘grads’) have the effect on half of the filter. The most common use for a graduated filter is to reduce the luminosity of a bright sky balancing it to the terrain below. The advantage of using a grad filter, rather than HDR techniques is a far more neutral colour representation than the “candy rainbow” side effect resulting from HDR processing. Plus, it’s far more authentic and satisfying to create a great image with a single exposure, and far less work in post processing too.
NB: Not compatible with the LEE filter system due to the glass being too thick.