I've broken down my review for you and them into reason for purchase, first impression, product test, suggestions for improvement, tips and conclusion. I hope this helps with clarity.

I received the product free of charge as a Vine product tester, but this has no effect on my review. I also only test things that I can usefully use myself and integrate into my everyday life.

Reason for purchase:
I ordered this filter for 2 reasons. The first reason is that if I only want to travel with light luggage, I don't want to bring my entire plug-in filter system with me. The second is that I can use it well in videography, where I usually film according to the 180 degree rule. This means that in order to obtain a cinematic video image with a certain amount of motion blur in the individual frame, you film with a shutter speed of 1/fps x 2, for example, I film at 50fps, so I need an exposure time of 1/100s, which is not possible without an ND filter, especially in the wide angle range when the sun is shining.

First impression:
The packaging looks very classy, but she is also welcome to do that, given the price that is called for the filter. The filter is in an equally pretty and high-quality filter bag, which I have never seen in this form with round filters before. With the tab on the side, you can lift the filter to prevent accidental contact with the glass when removed. The closure of the bag is magnetic. A nice gimmick is that the cardboard packaging of the filter can be transformed into a small picture frame.

Product test:
The filter is a dream to the touch, heavy (91g) and easy to grip, I also really like the contrasting adjustment aids. These can also be removed if you want to continue using a lens hood. This requires a small microtorx, e.g. from a precision engineering kit. When the filter is adjusted, it is buttery smooth across all stages.

In the test, the filter shows no weaknesses. As a result, I could not detect any color cast and there was no X-Cross effect. The promised effect of up to 5 aperture levels is maintained. Technically perfect and that is the most important aspect of an ND filter.

Suggestions for improvement:
1. The sustainability aspect, as taken up when using cardboard as a picture frame, could also be reflected in the filter bag by avoiding the use of animal products (leather).
2. An 82mm variant would be desirable and recommended, then the filter could also be used on (m) a 24-70mm/2.8, for example.

Tips:
It is always advisable to buy such a filter in the largest possible diameter so that you can adapt it to as many lenses as possible in your own fleet using step-down rings. Of course, this also eliminates the option of continuing to use a sun visor.

Conclusion:
Technically perfect filter in the upmarket price segment.

I hope my review was helpful in your decision making

Neutral density filters are an integral part of photography. They are used all the time, especially in landscape photography. You know these great pictures of flowing water that looks so “fluffy” soft — for something like that, for example, you need a neutral density filter.

A neutral density filter, or “ND filter” (neutral density filter), absorbs the light so that you can expose for longer. Because of this long exposure and the movement of the water, it looks so great.
Taking pictures with a neutral density filter darkens the incoming light and allows you to shoot better in very bright environments.
If you use a neutral density filter in bright environments, you can in return shoot with a wider aperture or longer shutter speeds.
You can achieve beautiful effects by taking pictures with a longer exposure time.
Pictures are usually overexposed if you choose a particularly long shutter speed.
With a neutral density filter, you can prevent this and take pictures with a long exposure time despite a lot of light.
As a result, movements become blurred and flow into one another.
For example, you can display water or clouds, as well as fast-moving objects, in a particularly creative way.

The K&F Concept Nano-X PRO series ND1000 filter impresses with excellent quality, it is delivered in a stylish case (magnetic closure). Includes a cleaning cloth.
I shot at the five pictures and numbered them. The difference is obvious.
The filter is worth the money, it is simply screwed on and even my lens protector still fits on it.
This filter makes you want more and gets full points from me!

Anyone who likes photography knows what you use an ND filter for. Since my attention is the landscape photography I can not avoid working with such filters. I ordered this one from K&F for my full frame camera.

I was just tired of filling my backpack with ND filters of different strengths. So the Nano-X Pro came in handy. To use it on several lenses I ordered it in the size 77 mm. I then work with step up rings to be able to use it on smaller lenses.

To say it right away: The optical quality and the quality of the images has flashed me! The workmanship is excellent and very successful. The lens thread is top clean cut.
The filter is adjustable from ND 2 to ND 32. The larger steps (f stops) are marked on the ring and easy to read. It can also only be turned in this range of 1-5. Below or above it does not work. So you always know by the stop what you have set.

The 77 mm. Ring brings 93 gr. on my kitchen scales. Everything is solid and feels very good. The setting runs well with slight resistance. So it should be.

The optical quality is absolutely flawless and even in difficult lighting conditions the filter delivers top. Chromatic aberration or color gradients into the green, magenta or anywhere else I have not been able to determine even when pixel peeping. Even with foliage or firs in backlight and with reflections from dew, the quality of the filter is unsurpassed. Finally a ND filter that does justice to my limited lenses and the full-frame sensor. The frame thickness with thread is only 9 mm. Without thread 0.63 mm. So you can use the filter on wide angle lenses without edge shading.

Thanks to the two screwed brass handles and the ribbing of the ring, the filter can be adjusted very sensitively.

Conclusion:
K&F Concept has delivered a top filter here. What good is it if you put thousands into lenses but then bad filters make the work difficult or lead to lousy results? From me clear 5 stars+. I hope this is useful for your purchase decision. Also the price is relative because you save at least 4 ND filters.

I was always of the opinion that a cheap filter set was sufficient. After this filter, my opinion has completely changed. The quality of the filter is excellent. I really didn't think that was possible. You might notice - I'm totally flashed by this filter... It is excellent quality and workmanship. The controller is made of metal and here alone you can tell how good the processing is.

You also have to remember that the photo quality is affected by filters. This is not the case with the K&F filter! The highlight here is that I don't need tens of different replacement filters, but can always adjust them directly to the respective situation. Personally, I still lack the stronger gradations of up to 10 apertures. However, I'm really so excited about this filter that I'll see if this filter is still available in 6-10 f-stops. I would definitely buy myself, even though I've worked with cheap filters around 50 EUR so far. Quality comes at a price and in this case it's true! But you really get something on offer here for its price.

By the way, the filter sits well on the lens and I'm not afraid that I would lose it. It is very easy to use. The neutral density filter comes in a nice bag and is therefore very well protected.

I already have a few filters at home, including the K&F Concept Nano-X ND Filter 77mm Variable Gray Filter ND2-32 for 75 euros, which I use on my wide-angle, for example in bright sunshine (for open aperture shots) and for long exposures and that is already really good.

Now I was allowed to test the variable ND filter from the PRO series of K&F, a filter for no less than 280 euros. Of course, if you already work with filters, you should also use high-quality glass on a high-quality lens, but a filter for just under 280 euros is not a pittance and this investment should be well considered. What I can say in any case: The filter is not only from the price level but also from the performance and workmanship at the top.

It starts with the presentation (packaging) of this filter, neatly processed bag with magnetic lid, suede applications, soft and lint-free lined inside, a lateral belt with which the filter is transported upwards by pulling.
The filter itself is extremely well made and with the two brass lugs it is easy to use.
It has a very nice resistance when adjusting, not too heavy and not too light.
The glass shows no flaws and the threads are also absolutely clean cut.
About the image quality / image performance I can only say: TOP!
There are no color errors/color cast or anything else negative here. So I can work with my lens in bright sunshine even with open aperture and if I like also with a slightly closed aperture with the help of the filter realize long exposures.
Image quality is as I said with me as good as if I had no filter at all on the lens and so it must be.
The pictures I uploaded (undemanding test shots) were taken with the aperture open and against the sun.

My conclusion on this filter:
Very high quality workmanship/image quality flawless/haptics excellent. Price very high
Now everyone must decide for themselves whether such an investment comes into question.

I've used ND filters from K&F in the past, so I wasn't surprised by the quality compared to newbies.

The filters allow sharp focus without any restrictions. Thanks to the really extremely thin glass and the thin frame, there is no cloudiness or dark spots at the edges. It is ideal that the filter has a thread mounted on the front, so that you can easily mount several of them one behind the other.

The frame has small brackets so that if you want to readjust it, you don't have fingers in the picture.

The ND Filter 67mm set is rounded off by a nice leather storage pouch. Overall, absolutely great!

The K & F Concept filter arrives here safely packaged. It comes with a duster and a bag for storage.

The workmanship of the filter is really first-class. High-quality materials, excellent handling, a perfect fit and not too heavy on the lens or in the hand.

The filter is simply attached to the lens using a rotating mechanism.

The filter conjures up wonderful images that you no longer have to rework.

The price is certainly a deterrent for now - but in my opinion, you get one of the best filters on the market here. Professionals MUST strike, amateur photographers CAN strike without hesitation

I had a few individual filters with me occasionally. But it was often too expensive for me to fiddle with it in nature. Screwing the filter together to obtain further adding gradations is also fiddly. There are enough individual ND filters, but each time you had to change the filter again...

With this filter here, you basically trick the entire handling process. I hadn't even found out that there was such a thing. That's why I've included a small video so that you can see the function. Even though “only” ND2-32 is available here, you can still see what these products can do.
Especially for experimenting, a matter of seconds, sometimes using a different filter setting. With low filter strengths, the automatic camera is also sufficient and you can see the current shutter speed when adjusting the filter. In this way, soft water structures can be created with relatively bright light or soft clouds in the sky, etc.pp. I didn't really notice stray lights or reflections, but I'm reworking something like that on a PC anyway.

The price of this product is high, but considering that it covers several filters at once, it's not too bad. However, the general question is what kind of filters do you really need. I've had an ND8 and an ND1000 so far. Sometimes an ND 4000 would have been required (to safely create “deserted” objects/spaces).

However, I find the concept here really innovative and practical.