The Kenko Vari-NDX filter is a variable neutral density that has a practical use filter factor range of 2.5-450, or a light loss of 1.3 – 8.5 stops.
Kenko created this filter by taking two pieces of the highest quality polarizing and mounting them in opposition to each other. When the filter ring is turned from min to max the filter darkens until it is nearly opaque. This has the effect of a neutral density filter that can change from a 1.3 stop light loss to a 8.5-stop light loss.
This type of neutral density filter is very valuable for controlling exposure, slowing down shutter speeds for creative blurring effects. This allows for shutter speeds as low as several seconds to be set in full sun conditions. It also allows for using very wide aperture settings like f/1.4 or f/1.8 for a very shallow depth of field in bright sunny conditions.
Traditionally when two polarizing filters are put together and used in this way there is an increase in color shifting as the neutral density effect increases. The Kenko variable NDX filter counters this problem by using a newly developed depolarizing plate in the construction of the filter to give it the most neutral color balance. This means very little to no color shifting in the recorded image. Color shifting is a problem with other variable ND filters on the market today but the Kenko Vari-NDX has broadcast quality color fidelity.
This filter has high-quality construction with durable aluminum filter rings and same sized filter thread on both the front and back.
The Kenko VARI-NDX is available in 77mm and 82mm sizes.