Singh-Ray's Vari-ND Variable Neutral Density Filter lets you continuously control the amount of light passing through your lens by as much as 8 exposure stops--with no loss of color fidelity or sharpness - without changing your filter.
The filter size is 82mm
The Vari-ND makes it easy to achieve slow shutter speeds of one or more seconds to "blur" the motion of falling water, passing clouds, flying birds, busy people, or any other moving subject within your scene.
The video DSLR folks will love this filter, too. Use it wide open on a fast prime like the Canon 50mm f1.2 or 35mm f1.4 and you'll be able to keep the shallow depth of field without the worry of overexposing the shot or changing ND filters constantly.
- Carry case.