This filter is beautifully crafted, and unlike many cheaper variable ND filters, the illumination is extremely even across the entire image from the brightest to the darkest setting. There are none of the strange bright and dark areas you get with many variable ND filters.

The scale can be adjusted over a range of four stops to give you exposure reduction between 1 and 5 stops. In my testing, I found it to be a little less than 5 stops at most, but it's pretty close. This allows you to open the aperture wider to get a shallower depth of field without having to change the shutter speed, which is especially useful when shooting video. For example, if you needed to shoot at f/16 to get a correct exposure without a filter, you could achieve the same exposure by shooting at around f/2.8 with the filter attached and at the darkest setting.

In my tests, I didn't notice any color cast from the filter, and the clarity of the glass is exceptionally good, so I'm not worried about any loss of sharpness.

It's pretty close to being the perfect ND filter.

TIP: If you need to use a filter on multiple lenses with different filter diameters, simply buy the filter with the maximum diameter you need and then use it with step-up rings on the smaller-diameter lenses. This is much cheaper than buying a filter for each lens diameter.