Formatt Graduated Neutral Density HD Filters enable the shooter to adjust exposure without affecting color 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
Heavier ND's can be manufactured but are not standard stock items
Neutral Density Filters Have Four Main Uses
To enable slow shutter speeds to be used, especially with high speed films, to record movement in subjects such as waterfalls, clouds, or cars
To decrease depth of field by allowing wider apertures to be used, which helps separate subjects from their background
To decrease the effective ISO of high speed film (above ISO 400) and allow it to be used outdoors in bright situations
To allow cine and video cameras (which have fixed shutter speeds) to film subjects such as snow, sand or other bright scenes which could cause overexposure
Neutral Density Factors
ND.3 (exposure adjustment = 1 stop, reduces ISO 1/2)
ND.6 (exposure adjustment = 2 stops, reduces ISO 1/4)
ND.9 (exposure adjustment = 3 stops, reduces ISO 1/8)
ND1.2 (exposure adjustment = 4 stops, reduces ISO 1/16)
Formatt Grads are Available in Four Types
Soft Edge - Half clear, half colored with a smooth transition to full density. Generally used with medium to wide angle lenses
Hard Edge - Half clear, half colored 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
Blender - The grad line is right at one edge of the filter so the color change runs from top to bottom. Perfect for irregular objects and skylines