Transparency notice:
The product was made available to me free of charge as an evaluation sample, free from any influence or expectations. My review is based solely on my personal assessment and experience of using the product.

Review:
For quick readers, I'll anticipate my review, below I'll explain the details of my decision making, my impressions of the product.

It is not difficult for me to give it a 5 star rating, because the ND filter meets my expectations accurately, its function is impeccable, the mechanical manufacturing quality is also more than convincing, not forgetting the useful and practical storage case.

One small thing bothers me in the product description, the suitability for 8K videos. What's the point, is that pure marketing? It seems that way. I find this advice unnecessary, because you could also say that you can also take photos with it, or is also suitable for color rendering, as well as for b/w. A useless statement.

I have a piece of workmanship in my hands and I can tell that from the first impression, purely from the mechanical quality. Wow, what a milled part, the mount ring. No material has been spared here, nor has the precision of its processing, so the fine thread is also precisely cut and, of course, there is no manufacturing residue on the filter.

The glass, which is high-quality coated optical glass, is absolutely pure and flat, with a straight and oblique view, rotating, I do not recognize any distortion, which is later confirmed in my photos too, and the sharpness of my lens is not adversely affected either.

For direct image comparison, I took a picture with a filter and one without on a tripod, of course with an adjusted exposure in each case. I left the aperture and time as I did, I adjusted the light difference via the sensor sensitivity on the ISO controller, and my premium class German full-frame camera offers plenty of work space.

I see almost no differences, only in contrast do I think the filter recognizes a minimally more inanimate image, slightly less brilliance. With regard to the shades, I recognize a slightly “colder” image, i.e. minimally bluish.

I can easily adjust both in the RAW Converter and I think these minor influences are acceptable, and I only recognize them in a direct comparison and you don't normally have them. As you would expect, K&F Concept really delivers quality.

I also really like the grip of the filter, so I can grip and unscrew it securely even now in winter with cold fingers, without having to worry about it slipping on my fingers.

For another smaller filter thread, I have a comparable ND filter from a well-known German brand, it is significantly more expensive and only slightly surpasses the image quality of the K&F Concept filter. Direct comparison is not possible, they are different lenses, which is why the filter diameter is different.

In conclusion, I fully recommend buying the K&F Concept ND filter. It clearly serves the premium class, at least the lower premium class; it clearly stands out in terms of quality from the cheap ND filters in the 20-30 € class.

Thanks for your attention while reading my review. If you would like, feel free to give me feedback or a “thumbs up”, I would be happy to hear from you.