K170 SkyEye Reverse GND 0.9 3 Stops 170x190mm

Reverse graduated ND (R-GND) filters are used to control the dynamic range within a scene at the time of capture.

In a landscape scene the sky is normally brighter than the foreground and at sunrise or sunset a fairly narrow band of light around the sun is far brighter, so a R-GND filter is inserted in front of the lens and moved to a position where the brighter part of the scene is covered by the Reverse GND filter and the margin between sky and sun, together with the margin between the sun and foreground is faded using the transition areas of the R-GND filter.  

The scene is normally metered for highlight area and shadow area and the difference in stops dictate the strength of filter used.  The use of a R-GND filter avoids the heavy darkening of the sky, normally associated with the use of stronger GND filters in sunrise and sunset scenes. The so called transition areas are normally soft.