Formatt Graduated Neutral Density filters enable the shooter to adjust exposure without affecting colour balance. Exposure can be increased by 1,2,3 or 4 stops to suit individual situations.
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 don't have total light control, as in bright contrasty landscapes. Exposing for the foreground will produce a washed-out, over-exposed sky while exposing for the sky will leave the foreground dark and under-exposed. This filter enables cloud detail to be kept correctly exposed in the picture.
Soft/hard indicates the degree of transition
A standard set of ND's is 0.3, 0.6, 0.9 and 1.2. This represents 1 to 4 stops of light reduction
Note:
Heavier ND's can be manufactured but are not standard stock items
Formatt Grads are available in four types
Soft Edge - Half clear, half coloured with a smooth transition to full density. Generally used with medium to wide angle lenses
Hard Edge - Half clear, half coloured with a definite less subtle transition. For use with long focal length lenses
Razor Edge - As hard edge but with a solid transition line for shooting corners of buildings, knife-edge horizons or when a very bold transition is required
Attenuator/Blender - The grad line is right at one edge of the filter so the colour change runs from top to bottom. Perfect for irregular objects and skylines