Anyone who enjoys photography knows what an ND filter is used for. Since my focus is landscape photography, I can't avoid working with filters like this. I ordered this one from K&F for my full-frame camera. I was simply fed up with always filling my backpack with ND filters of varying strengths. That's when the Nano-X came in handy. I ordered it in 52 mm. I then work with step-up rings so that I can also use it on smaller lenses. To put it straight away: The optical quality and the quality of the images won me over! The workmanship is outstanding and very well done. The lens thread has a very clean cut. The filter is adjustable from ND 3 to ND 1000. The larger steps (f-stops) are marked on the ring and are easy to read. This way you know what you have set. The 52 mm filter weighs 28 g on my kitchen scale. Everything is solid and feels very good. The adjustment works well with slight resistance. That's how it should be. The optical quality is absolutely flawless, and even in difficult lighting conditions, the filter performs top-notch. Even when pixel-peeping, I couldn't detect any chromatic aberration or color gradients toward green, magenta, or anywhere else. Even with backlit foliage or fir trees and dew reflections, the filter's quality is unsurpassed. Finally, an ND filter that does justice to my limited lenses and full-frame sensor. The frame thickness with the thread is only 10 mm. Without the thread, it's 0.75 mm. This means I can also use the filter on wider-angle lenses without vignetting. Thanks to the screwed grip and the knurling on the ring, the filter can be adjusted very precisely. Conclusion: K&F Concept has delivered a top-notch filter. What's the point of investing thousands in lenses if bad filters make the work difficult or lead to poor results? A clear 5 stars from me. I hope this is helpful for your purchasing decision. The price is also put into perspective, as you save yourself at least four ND filters.