I already have a few filters at home, including the K&F Concept Nano-X ND Filter 77mm Variable Grey Filter ND2-32 for 75 euros, which I use on my wide angle, e.g. in bright sunshine (for open glare shots) and for long exposures, and it's really good.

Now I was able to test the variable ND filter from K&F's PRO series, a filter for just under 280 euros. Of course, if you are already working 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 cardboard stick and this investment should be well considered. What I can definitely say is that the filter is at the top not only in terms of price level but also in terms of performance and workmanship.

It starts with the presentation (packaging) of this filter, cleanly finished bag with magnetic lid, suede appliqués, soft and lint-free lined interior, a sideways strap with which the filter is moved upwards by pull.
The filter itself is extremely well made and can also be operated with the two brass noses.
It has a very pleasant resistance when adjusted, not too heavy and not too light.
The glass shows no flaws and the threads are also cut absolutely cleanly.
As for image quality/performance, I can only say: TOP!
There are no color errors/color tint or anything else negative here. I can therefore also work with my lens with an open aperture in bright sunshine and, if I like, take long exposures with the help of the filter with a slightly closed aperture.
As I said, image quality is as good as if I had no filter on my lens at all and that's the way it must be.
The pictures I uploaded (undemanding test shots) were taken with an open aperture and against the sun.

My conclusion about this filter:
Very high-quality processing/error-free picture/excellent feel. Price very high
It is now up to everyone to decide for themselves whether such an investment is an option.

Flexible light control with two handles without changing filters - infinitely variable neutral density filter perfect for reducing the amount of incoming light (1 to 5 stops) without affecting colors and contrast, 8k video recording.

The frame is made of brass material, CNC pattern design, which significantly improves hardness and flexibility, and the installation is smooth and durable, otherwise self-locking frame technology, 1-5 precise light reduction adjustment!

The K&F Concept coating technology gives the filter a very low reflectivity of 0.15%, which ensures good light transmission, reduces stray light and ghosting, prevents glare and does not affect the original lens performance!

Double-sided 36-layer nano coating, waterproof, dirt-proof and scratch-resistant, for excellent filter durability!

The frame adopts an ultra-thin design, 0.01 mm processing accuracy, is very well adjusted and fixed to the lens, so there are no dark corners when attached to wide-angle and telephoto lenses.

The storage bag is made from genuine leather material, purely handmade, specially produced for K&F Concept photographers!

I'm very satisfied

My buddy and I have been running a channel on Youtube for several years and have also become partially self-employed through it. We produce content for companies and we have now put together a lot of equipment for this purpose. When it comes to ND filters, we have been in the cheap segment so far and have relied on fixed filters, as we haven't heard anything good about the cheap variable filters.

We now use square filters with matte boxes for larger productions. But especially for smaller orders, where we need a lot of flexibility, we rely 100% on the Nano-X Pro. This covers exactly the area that we need. The optical quality of the images is really great and there is simply no falsification. In some cases, we also use an adapter for square filters after the Pro ND. This works because the Nano-X Pro has a thread into which you can screw additional filters.

In theory, it is even possible to use it in conjunction with a matte box and a rectangular filter. The options are very varied.

I can only say words of admiration about the workmanship, simply terrific. As soon as I unpack it, I have the feeling that I am holding a super high-quality product in my hands. The workmanship is impeccable and the case makes an equally high-quality impression. The adjustment of the filter is very smooth and the filter has not even tilted so far.

I can make my recommendation without hesitation. Anyone who makes the, admittedly quite large, investment will be rewarded with quality and visual material, which definitely justifies the price. Anyone who claims that a cheap filter does the same in this regard has not yet addressed this issue in detail.

This variable ND filter from the K&F Concept brand was kindly made available to me free of charge as part of the K&F Concept Vine program. First of all, I would like to thank K&F Concept and, of course, the manufacturer.
However, the fact that I received this product free of charge has no effect on my review.

First of all, you have to say that you get an incredibly well-designed product here, which is reflected in the type of packaging. It is very high-quality and attractively designed and gives you the feeling that you have received a quality product here. In particular, the storage bag with magnetic closure is a really nice bonus that you don't often get included in this quality. With a simple strap on the side, the filter can be pushed up from the pocket and removed.
It is also very nice and a nice idea that you can reuse the inlay of the packaging as a small picture frame. A small cardboard sheet is included for folding, on which the quick instructions for folding are also printed directly. This then becomes a small stand, which can be glued directly to the back of the inlay. The small but somewhat stylish picture frame is ready

have broken down my evaluation 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 for free as a Vine product tester, but this does not affect my rating. I only test things that I can use sensibly and integrate into my everyday life. Reason for purchase: I ordered this filter for 2 reasons. The first reason is that if I just want to travel light, I don't want to take my complete cartridge filter system with me. Secondly, I can use it well in videography, where I usually film according to the 180 degree rule. This means that in order to get a cinematic video image with a certain degree of motion blur in the individual image, you film e.g. B. with a shutter speed of 1/fps x 2, I'm filming at 50fps, so I need an exposure time of 1/100s, which is not possible without an ND filter, especially at wide angle in sunshine. First impression: the packaging looks very classy, but given the asking price for the filter, it is allowed to do so. The filter is in an equally pretty and high-quality filter bag, which I have never seen in this form with round filters. The tab on the side allows you to lift the filter to avoid accidental contact with the glass when removing it. 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 feels like a dream, heavy (91g) and easy to grip, I also really like the color-contrasting adjustment aids. These can also be removed if you wish to continue using a lens hood. For this you need a small Microtorx, eg from a precision mechanical kit. When the filter is set, it runs buttery smooth across all stages. The filter showed no weaknesses in the test. As a result, I could not detect any color cast and there was also no X-Cross effect. The promised effect of up to 5 f-stops is retained. Technically perfect and that is the most important aspect of an ND filter. Suggestions for improvement: 1. The sustainability aspect, as taken up when cardboard is used as a picture frame, could also be reflected in the filter bag by not using animal products (leather). 2. An 82mm variant would be desirable and recommendable, 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 with the largest possible diameter so that you can adapt it to as many lenses in your own fleet as possible using step-down rings. Of course, this also eliminates the possibility of continuing to use a sun visor. Conclusion: Technically flawless filter in the upper price segment. I hope my review was helpful in your decision making.

was always of the opinion that a cheap filter set was sufficient. After this filter, my opinion completely changed. The quality of the filter is excellent. I really didn't think that was possible, totally flashed by this filter... Quality and workmanship is excellent. The controller is made of metal and here alone you can tell how good the workmanship is. You also have to keep in mind that photo quality is affected by filters. This is not the case with the K&F filter! The highlight is that I don't need umpteen different replacement filters, but can always adapt them directly to the respective situation. Personally, I still miss the stronger gradations of up to 10 apertures. However, I am really so enthusiastic about this filter that I will see if this filter is still available in 6-10 f-stops. I would definitely buy one, even if I've worked with cheap filters around 50 EUR so far. Quality has its price and in this case it is true! But for the price you really get something here. By the way, the filter fits well on the lens and I'm not afraid of losing it. It's very easy to use. The gray filter comes in a nice bag and is therefore very well protected.

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'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!

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