In landscape photography, it is helpful to have three specific lens filters in your camera bag. These are the circular polarizer (CPL) filter, the neutral density (ND) filter, and the graduated neutral density filter (GND).
Using a graduated neutral density (GND) filter is fairly easy and doesn’t require any advanced techniques in post-production, but the easiest option isn’t always the best choice; due to the filter’s transition being horizontal, anything above the distinction will be darkened and anything below will be left alone.
Aurora Aperture has just announced what it claims is the world's first variable graduated neutral density filter. It's a family of filters called the Aurora PowerGXND.
Tempered glass is a toughened form of glass used in car windows, shower doors, refrigerator trays, and mobile screen protectors—and now Breakthrough Photography are using it to create their new Dark CPL and X4 GND filters.