Claiming to be the world's first Variable Graduated ND (Neutral Density) Filter, the PowerGXND offer a continuous variable range between 0-5 stops over half of the lens. This lens can be shifted to be positioned over parts of the image so you can conveniently dial in a perfect exposure for both highlights and shadows.
Gradual ND filters already exist, but they only have fixed values. The PowerGXND filter by Aurora Aperture offers the convenience of being able to change the amount of light coming through with a twist of the dial ring.
The video above shows the variable change in real-time video.
The design includes hard stops for minimum and max variability as well as markers for each stop of light change.
There is also a range of slim adapters available so you can rotate and move up and down to select the appropriate position for blocking the light.
Check out their Kickstarter campaign for more info: kickstarter.com/aurora-aperture
If you don't want to fork out the cash for something like this, there are software solutions like Sony's Digital Filter app which allows you to expose different parts of the image as well as change white balance. Although it only works for Sony Cameras - digislider.co.uk/blog
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