I'm no pro, but this filter is very good.

I received the new X-PRO filter set today and have already tested its applicability in the apartment. A judgment on the quality of the filter glasses and the combinability in a shot I still deliver ... The supplied box holds the holder + adapter rings + CPL + ND 8/64/1000. At the drawstring you can pull out the compartments and then very conveniently remove the filters. The plastic filter frames are decently sharp-edged, but not unpleasantly so, and allow you to remove and handle the filter without having to touch the glass. The tabs on the frame also make it very convenient to pull the filters back out of the holder, especially in any order. I have ordered two empty frames in 100 X 150 on the manufacturer's site, which should take my graduated filters after receipt, which I have from another manufacturer. I am curious how well this will work. If it works out, I'll have a complete system for myself, with CPL, three ND filters and two graduated filters (Soft 0.9 and Reverse Soft 0.9). Sliding the filters in and out of the holder requires some force, but is neither awkward nor imprecise. This will then also allow the graduated filter to be aligned well. The handling of the CPL filter with the insertion bracket is great, the turning mechanism is a bit rough, but precise. Screwing the adapter rings onto the lens goes very well, the threads are cleanly made, nothing rubs. Attaching the holder to the adapter ring is also a pleasure and the existing locking screw is very welcome, as the holder can be rotated relatively easily on the ring. The handling of the system has already convinced me, with "only" two slots I can live well for my needs and I look forward to the first use, in the next few days, in the great outdoors and with cold fingers. I have so far worked with round screw filters and waived graduated filters, which I now want to change. I also looked at the system from Rollei (Mark II), which can not keep up with the X-PRO from K+F in handling. Everything very flat and fiddly, offers little surface for holding and joining the parts. Getting the polarizing filter or adapter ring out of the holder again is no fun and almost impossible with cold fingers. K&F has solved this much better. Who wants to use graduated filters is very well served with the X-PRO set, who only needs gray filters, I would advise a magnetic round filter set, whose diameter is well above its largest lens, which is even faster to use, is more compact and should then not darken with several filters in parallel.

If I'm honest, I've always relied on established brand manufacturers such as e.g. B&W or Rodenstock set. Although I also have a few filters from Kase and K&F in my inventory, I didn't really have Asian manufacturers on the screen when it came to filters.
And that's exactly what K&F wants to change with the Nano-X Pro series.
K&F has meanwhile gained a pretty good reputation in the circles of photographers and this is not least due to the very interesting price-performance ratio which K&F products usually offer .
And now K&F seems to be reaching for the stars and with the Concept Nano-X PRO series they also want to reach the part of the customers who rely on high-quality products and are willing to dig deep into their pockets accordingly.
I tried to find out whether this works with the Nano-X PRO CPL polarizing filter.

As already mentioned, K&F wants to reach the pro users with the Concept Nano-X PRO series and they usually rely on filters from well-known brands and then charge a correspondingly high price for them.
And that K&F is quite capable of producing good filters, I could already see that when trying out the magnetic set and also some plate filters. Of course you had to show a little willingness to compromise here and there, but that was quite bearable, especially given that the filters had previously been in the cheap segment.
This looks completely different with the Nano-X PRO series, here K&F has to deliver unconditionally if they want to do justice to the price.
And yes, they do... starting with the materials, the processing and the quality of the coating, with the Nano-X PRO series, K&F no longer makes any compromises and shows what is technically possible. Gone are the days of stiff threads or seized filters! The ultra-precisely manufactured brass mounts of the Nano-X Pro series run butter-soft and convey the feel of a Peter McKinnon Polar Pro filter. No, that's not blasphemy, comparing these outrageously expensive premium filters with a K&F product. Quite the opposite, it actually
shows only very clear what the engineers at K&F are capable of if you give them free rein

to the filter itself...
I don't want to go into too much detail about the function of a polarizing filter here, that should actually be clear and also the fact that the polarizing filter is one of the filters whose effect cannot be added later in post-processing. It is therefore often said that a polarizing filter is the first and often the only filter that you really need.
The K&F CPL polarizing filter from the Nano-X series tested here plays in a qualitative league with the established brands and must don't hide behind them in any aspect. You don't have to compromise in any category here, really in any. I've never had such a good polarizing filter in my hands, and I'm saying that even though I have an outrageously expensive polarizing filter in stock, both from Rodenstock and from Kase.
The K&F runs so smoothly as if ball bearings were installed and thanks to the milled, really non-slip edge, the filter can also be gripped very well when turning. Of course, an attached lens hood makes it difficult to turn the filter, but that's not a fault with the filter! This is the case with every adjustable filter and many of my lenses have a kind of window in the lens hood for exactly this purpose, through which you can access the filter and adjust it without having to reach through the lens hood from the front.

The K&F also plays at the highest level optically and I could not find any negative effects on the finished picture. It does not visibly distort colors, nor does it significantly increase susceptibility to flares and ghosting. The only noticeable difference, the K&F eats a few more EVs of light, like my Rodenstock polarizing filter, and the tint is about the same as my Kase polarizing filter.
That is of course a matter of taste and one likes very translucent filters and the other likes it to be a little more tinted. Therefore I weigh this point, which K&F does not see as a negative point on the subject of packaging

...
Personally, I prefer a narrow, light plastic case, like these super noble magnetic closure bags used by K&F, but even there you can see the innovative strength that prevails at K&F and the incredible value that K&F places on details. Since I like this kind of thing very much and place a lot of value on small, useful details, K&F already gets a few bonus points from me for the packaging.
If there really is someone who uses the box as a picture frame, as K&F intended, dare that To be honest, I doubt it, but ok, the idea is very nice and a picture frame support that can be folded in origami style is in the box under the filter and cleaning cloth, already in summary

...
Uncompromising, from start to finish, so that with the K&F Nano-X Pro, you don't need to ask yourself whether there might be a better filter, just how to explain this issue at home in the most gentle way

K&F Concept Mini 3 Pro ND Filter

Good contrasts are the basis for beautiful, rich images. With the ND filters from K&F Concept you get a very high-quality and good set. The filters can be attached easily and without any problems. I could not determine any negative image effects such as color fringes.

If you want to take great high-contrast pictures, you can use the ND Filter Set from K&F Concept. Good quality, versatile and good price.

I simply copied the complete text from my YouTube video for you. Who prefers to see the video "Dji Osmo Action 3 I without ND filter in automatic mode and in PRO mode?" Enter on YouTube. Why do you need filters? It's a valid question, of course, who hasn't asked themselves that? I think everyone has stumbled across this topic and this question... The answer to this is very simple and surprising in view of this video - No, you don't need filters on a camera, it works without it...***but...It would be more an advantage as a disadvantage to have and use some. Anyone who works a lot on the water and beach, like me, or of course, like most of you, vacations there, quickly learns to appreciate filters. First, they are a very good protection against dust or sand from the beach. Of course, a filter also protects the lens, the lens in the camera. So much for the obvious, but the main job of a filter is to let less light through onto the sensor, it's like putting sunglasses on the camera. This has the advantage that longer exposure times can be achieved. It helps the camera to adjust and react faster in automatic mode when controlling the exposure time or white balance. Or if you prefer to work in Pro mode, you will quickly find that the exposure, the shutter, generally works better. In general, filters make the water smoother, and there are also fewer reflections. Or if you take great landscape shots, the sky immediately looks a little bluer. Filters also enhance the colors generally, making them more vibrant. DJI has, in my opinion, excellent colors and that in connection with a filter automatically makes the recordings **//LVL UP. This saves you having to color the film material because it comes out of the camera almost finished. Of course, the full professionals among you have other requirements and such, but I'm talking here for the normal user, like you and me... There are different ND filters. It starts **in my set at ND 4 and goes up to ND32. The ND4 filter lets only ¼ of the light through to the sensor and the ND32 filter 1/32. I use my filters like this... in the morning ND4, towards noon ND8, noon to afternoon ND16 and afternoon to late afternoon when the sun is very high ND32, and then in the evening just before the golden hour I go down again with the filter strengths. Over time, you will figure out when and where which filter is best used, is not witchcraft, even if many want you to believe that. Especially in summer or in winter when there is snow, I think it should at least be almost mandatory to have ND filters to have. If you like to film in Pro mode and work a lot with it, it is almost a must to work with filters alone because otherwise you cannot work with exposures in a meaningful way.... Especially in summer or in winter when there is snow, I think it should at least be almost mandatory to have ND filters with you. If you like to film in Pro mode and work a lot with it, it is almost a must to work with filters alone because otherwise you cannot work with exposures in a meaningful way.... Especially in summer or in winter when there is snow, I think it should at least be almost mandatory to have ND filters with you. If you like to film in Pro mode and work a lot with it, it is almost a must to work with filters alone because otherwise you cannot work with exposures in a meaningful way....

K&F Concept Mini 3 Pro CPL ND Filter

Good contrasts are the basis for beautiful, rich images. With the ND filters from K&F Concept you get a very high-quality and good set. The filters can be attached easily and without any problems. I could not determine any negative image effects such as color fringes.

If you want to take great high-contrast pictures, you can use the ND Filter Set from K&F Concept. Good quality, versatile and good price.

When I ordered the K&F variable ND filter, I wasn’t sure what to expect in terms of quality and the coloring that would be achieved when my images were rendered. However, the colors do not shift at all, and I was pleased with how nicely they pair with the Sony A7iii and A7riii. As an owner of both Polar Pro and Tiffen filters, I must say this filter is a cost-efficient product, coming in at half the cost of the Polar Pro filters I own. Even better, is that this filter has hard stops so you don't get that X when you go beyond the filter’s limit. If you're on the fence about ordering this product, I highly recommend trying it out. Below, I've added a couple images where the K&F variable ND filter was utilized- one shows the filter on my Sigma 135mm f/1.8 Art, and the other demonstrates a portrait I took while using it.

Perfect pro mist filter.