This K&F Concept 67mm Variable Fader ND and CPL Lens Filter is a really good, adaptable lens filter that combines two common lens filters into one with a variable adjustment. I was immediately impressed by how smooth the filter was. The adjustment itself is smooth and tight and the actual transition of the image is smooth to match it. The quality seems very good overall and it threaded smoothly onto my lens.

One note, I did not realize ahead of time is that you will need a different lens cap to fit on with the new filter. I have a 67mm lens and ordered the 67mm lens filter. My original lens cap does not fit on the new filter, so I now need a 72mm lens cap to go on this. There is a chart buried in the product description that shows the adapted lens cap size for each filter size but it is essentially a standard size up from whatever filter size you order. These are fairly inexpensive and easy to come by, but it would have been nice to include a corresponding lens cap with the product.

There are many applications where this comes in very handy and can allow you to get unique shots that would be difficult or impossible without this. Some applications would include scenarios like:
- mixed lighting conditions with bright and shadowed areas to balance the exposure;
- removing glare and reflections on reflective surfaces like water;
- landscape photography to reduce glare and improve the appearance of the sky; and
- taking long exposures in brighter conditions without overexposure.

The filter set to minimum does darken the image slightly. Also hoods and other accessories do not fit with this filter, so there are instances where you'll want this off the camera, such as low-light conditions. Still, this is a great all around filter that is worth having in your bag.

Overall I am very happy with the quality and function of this K&F Concept filter and would highly recommend it. Do keep in mind that you'll need a larger lens cap diameter than the size you order, but other than that I think this is a very worthwhile pick.