Variable ND filters aren’t exactly a new thing. Neither are polarisers. In fact, without polarisers, variable ND filters wouldn’t even exist. Pretty much all variable ND filters are the result of cross-polarisation, stacking two polarising filters on top of each other with their relative angles to each other controlling the light that goes through. As such, all Variable ND filters are also polarisers. But most have one big problem. You can’t rotate the polarisation.
There are one or two filters on the market to overcome this, that allow you to rotate the polarisation independent of the overall exposure. And now there’s another one, as Haida has announced its new PROII CPL-VND 2-in-1 filter with 3-7 stops of variable ND stopping power along with a handle that lets you rotate the polarization while maintaining your level of neutral density.