K&F Concept Nano-X variable ND with thread vs. K&F Concept Nano-X Magnetic vs. Freewell variable ND with thread

Looking for a variable ND filter for wide angles up to 24 mm focal length (APS-C 16 mm) I have the three filters ordered from amazon.de. Since prices are constantly changing, I just want to name the order. The K&F Concept Nano-X ND with thread is the cheapest, the K&F Concept Nano-X Magnetic is the middle priced one and the Freewell with 77mm thread is the most expensive.

I took photos with the 3 filters on the brand new Nikkor Z 4 / 24-120 mm and the Fujinon 2.8 / 16-55 mm.

The darkening of the K&F Concept Nano-X ND and K&F Concept Nano-X Magnetic are identical. The Freewell starts with a slightly stronger darkening. About 1/4 stop or time.

The 3 filters differ significantly in terms of vignetting (dark image corners). The K&F Concept Nano-X Magnetic performs worst on the Nikkor Z 4 / 24-120 mm with a focal length of 24 mm (see photo). If it absolutely has to be magnetic, I would go for a larger filter diameter and use a reduction ring. The K&F Concept Nano-X ND vignettes a little less (not at all on the Fuji 2.8 / 16-55 mm). The variable ND filter from Freewell achieves the best vignetting results thanks to its very flat design.

I find the K&F Concept Nano-X ND best packaged for transport. Here you get a nice round box with snapper. I liked the square plastic box from Freewell the least, but you can buy a very good (artificial) leather box with a zipper for a total of 5 filters from Freewell.

I am happy if my contribution is considered helpful and makes the decision easier.