Since I started testing K&F filters, I have become a big fan of the company. The quality of the filters and construction are excellent. The glass was of exceptional optical clarity and the brass rings are precision machined. I have never had any problems with cross threading or pulling off. The filters go on very smoothly and come off just as smoothly.

They are all filters that have just enough friction to stay where you put them, but they turn buttery smooth on the camera so you don't have to worry about moving your camera around on the tripod. They are just a real joy to use. This Euler filter per check mark has corresponding markings on the edge so you know which stop you're at, and it has a little tab that makes it easy to rotate the filter. It is very unobtrusive and should not interfere with your image, i.e. no vignetting.

In the old days, one problem with variable neutral density filters was that you would see this artifact of the two polarized plates crossing and these optical "X" artifacts in your image. I believe the newer ones used spiral circular polarization so you get an image without artifacts.

This filter does exactly what it is supposed to do, darken your image to allow longer exposures, or just block out extreme light and glare on a very bright day.

One thing that strikes me about this filter is that its metering is extremely accurate. If you say it for four stops and then take it off and lower your camera by stops, the lighting will appear identical, although there will be a little more glare without the filter because the polarization also reduces the glare.

Another optically perfect excellent filter from K&F.