In the past, I have only used ND filters with a fixed light reduction. While a fixed light reduction filter is far less complicated and, thus, less likely to add reduce image quality, you have to have several of them in varying strengths if you want to be able to use them in different lighting conditions and end up with the same camera settings. A variable ND filter allows you to adjust the light reduction without changing filters.

This one is machined very nicely and rotates smoothly. In my initial testing I didn't notice any image degradation. It does appear to add some warmth to the image but that is easily adjustable in photo editing. I have to do additional testing to see if the black X will be an issue. (The listing did point out that this variable ND filter can produce the black X when used at higher densities. There are more expensive variable ND filters that say they don't produce that affect.)

By nature of the way they work, a variable ND filter is larger in diameter than the lens it is attached to so the normal lens cap doesn't fit. This means you'll have to buy a larger diameter lens cap if you want to use one when this filter is mounted to your lens.

This is a versatile tool to add to my camera bag. I'll do some additional testing and, if I notice any issues, I'll update this review.