Hi Def filters do not experience color shift. They are specifically designed for use with High Definition filming and are optically consistent from filter to filter
The Formatt range of Neutral Density Graduated filters enables the shooter to adjust exposure without affecting colour balance. Exposure can be increased by 1,2,3 or 4 stops to suit individual situations. For example, when photographing landscapes in which the sky is much brighter than the foreground, placing the neutral density part of the filter onto the sky in the frame will reduce the sky exposure without affecting the foreground. This enables cloud detail to be kept correctly exposed in the picture.
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.
Formatt manufacture Neutral Density Graduated filters as Soft Edge, Hard Edge, Razor Edge and Blender / Attenuator.