Singh-Ray Variable Neutral Density Filter - 77mm Thin-Frame
This adjustable neutral density filter lets you adjust the Neutral Density affect by simply spinning the end of the filter, similar to how a circular polarizer operates. It gives you control over 8 stops of light.
These filters are very popular for sunsets, where you need to keep the shutter open long enough to expose the foreground without overexposing the background.
For more info, visit the manufacturer's site
- This is the thin-frame version of this filter. It is exactly the same as the regular frame version, except the metal frame protrudes a shorter distance from the end of the lens, making it more suitable for use with extremely wide-angle lenses where the frame may otherwise cause the image to vignette. The 77mm regular frame version can found here.