GradFilter simulates a graduated neutral density filter. GradFilter Pro extends support to allow multiple graduated filters of any color, on any layer. Either plugin can be used, for example, to darken a bright sky or brighten a dark subject so that both the sky and subject are properly exposed. In an ideal world, a real physical filter would be used as this maximises the dynamic range of the image hitting the film plane/sensor, but this plugin is still quite useful in many situations where one doesn't have such a filter to hand, especially when working with RAW files. In some ways, the plugin provides a greater amount of flexibility, by stretching the physical constraints of a real filter to allow the "addition" of light.

GradFilter is available for free and includes a functional set of features for applying a graduated neutral density filter to the main layer.