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The most important to me: the colour accuracy! By the way I did not check with vectorscope but I think this filter performs well! Especially in the middle range (3-7 stops). And this is what I need in strong sun: I don't use the lower end because that's not enough and I also don't need the strongest stops because that is too dark.
K&F Concept made well. I planning to buy from this filter in 72mm or 77mm size in the future.

I gave it try to this filter and I have to say: in this price range this is a very good value! Not perfect of course but decent.
This item performs best in the middle. The first 3-4 stops has a bit yellowish tint but above that is disappear.
From 8 stops slightly vignetting is coming with an average focal length. When you use wide angle or super wide lens, the vignetting (cross pattern) is coming strongly. But every vnd filter has the same problem with wide lenses!
With telephoto lens I did not see any degradation, image quality problems. Somebody say vnd filters in strong (high) stops has "double" effect and similar issues but not with this product.

As long as you know you won't likely be able to use the full range, this is a good deal (see video). The "X" pattern is almost certainly a sure thing with this kind of range. Still, the price is right.

Preso questo filtro ND variabile per l'obiettivo 18-55 con 52mm di diametro della mia Nikon si è rivelato perfettamente compatibile con il diametro dell'obiettivo dichiarato e si avvita senza problemi.
Si tratta di un filtro variabile, che consente di ridurre la luce in modo graduale, da 2 stop fino a 11 stop.
Ho trovato molto utile la possibilità di regolare la densità del filtro in modo graduale. Questo mi ha consentito di ottenere risultati ottimali in situazioni diverse, senza dover cambiare filtro ogni volta.

Nelle foto allegate si può vedere la differenza tra la foto senza filtro e quella con filtro applicato e il tempo di esposizione più lungo.
Le prove allegate sono state fatte con tempi di esposizione tra i 2 e gli 8 secondi.
Ovviamente per raggiungere ottimi risultati ci vuole molta pratica e bisogna saper utilizzare il fuoco manuale perchè una volta inserito il filtro se si riduce di molto la luce l'obiettivo ha difficoltà a mettere a fuoco in automatico.
Per il momento sono molto soddisfatto e mi sento di consigliarlo.

This filter is great. I've used static filters quite a bit but haven't used variables much. I love the motion of this one it glides very nicely. It has a great result and is well made. It doesn't add much weight to my camera either. And the carrying case is a nice addition since I don't leave it on my camera all of the time. Its a nice product and would definitely buy again.

This variable ND filter by K&F Concept is really well made. The threads and fit are perfect and the optical quality is better than I would expect at this price point. I like the convenience that a variable ND filter provides and this one has enough of a range to meet all of my needs. There are no hard stops on the setting, but the rings are stiff enough to stay where I set it and I don't have to worry about accidentally changing the setting if I bump it. As with other K&F Concept products, the included individually packaged cleaning cloths are also a nice addition. Overall, I'm very happy with this filter.

This filter is very made of aluminum, slim and very light. Very well constructed.
Because this filter is 52mm , but designed to fit a 50mm size lens, you will not be able to :
1. attach your lens cap (maybe a 52mm lens cap would fit)
2. attach your lens hood
3. attach any other filters to this one. You are able to attach 50mm filters to your lens, and then stack THIS one onto those filters. I did this with my CPL filter, but found it difficult because I had to rotate the CPL , and then rotate the Variable ND filter, so I removed the CPL for now.
Also, I need to investigate whether it is even advisable to use a CPL and ND together because of the low-light.

It is really a nice feature of this filter to incorporate 1 to 11 stops on this one variable filter. It makes it easy to dial to the stop that you want to use, but I found it a little confusing. The stops are labeled with Min on one end, Max on the other , and 8 dots in between.
So I'm not really sure what dot corresponds to what ND stop, there are supposed to be 11 stops, but there are only 10 markings.
Also , there is no lock at the beginning or end of the 10 stop markings.

Anyway , I've been experimenting and getting to learn how to use it.
I see how it it very convenient to have only ONE Variable filter, instead of several. Much less exptensive, much less complicated. But it is going to take me a little bit of time to learn how to use it efficiently.

I’ve mainly been using this ND filter on my Rokinon 16mm T/2.2 cine lens and it works like a charm. No weird color shifting or distortion to my images. Easily screws on/off, smooth rotating ring. No hard stops, but that’s to be expected from a budget friendly filter. Overall I’ve grown to love K&F products and this ND works great & has more than enough stops to help me achieve the proper exposure

There wasn't a 43mm available so I ordered the closest option, which was the 49mm and used a step-up ring to fit it to my EF-M 22mm. There is a slight greenish tint to the glass, though it does not colour the footage significantly enough to trouble me. Unlike some other variable ND filters I've used, this one does not produce a dramatic X at the end of the range, though some slight X-ing is present when going beyond the maximum.

I am leaving this filter on my 22mm permanently. FYI if you want to add a lens cap to this you will need a 52mm cap.