I ordered this K&F Concept 82mm Black Diffusion Mist 1/4 & Variable ND2-32 in-1 Filter to use with my Fuji GFX100s.

I love my Fuji GFX, but GF lenses are so sharp that they can be problematic for portraiture. A diffusion filter can produce results that require far less editing. This filter is dual use -- it offers a 1/4 strength diffusion filter with a variable ND2-32 neutral density filter.

I've used many different variable ND filters before. They all share one characteristic: at the highest ND setting, they produce a black X across the entire image. That does not happen with this filter. Has K&F Concept discovered a new technology for variable ND filters? No. They eliminate the X by limiting how far you can rotate the ND filter. In other words, this filter could produce an even heavier reduction in light, but a hard stop on the filter prevents you from accessing it and, consequently, from reaching the point at which the X will appear.

At its max, the ND filter will provide a 5 stop reduction in exposure. This is sufficient to allow for wide open apertures or relatively slow shutter speeds in anything but the brightest light.

The filter itself seems well constructed. It screws on and off easily and smoothly. Even when tightened down, the filter could be removed without having to resort to a filter wrench. Rotating the ND filter is smooth, and the filter holds its position. Coatings are well done; I did not notice additional flare when the filter was attached. I used this on a 20-35mm lens and did not get any vignetting. I can't say that the filter maintains sharpness because it is designed to reduce sharpness.

All in all, this is a useful filter to add to your kit.