I was afraid I would have problems being a variable ND with rare effects, and zero problems. Neither on the corners, nor at ND400, the truth is that a pleasant surprise for its price. It may have a little green tint, but with a correction of nothing in the Premiere I fixed it, between 5 and 10 points on the dye tab towards magenta and you're done. Highly recommended, you just need to have a cap like the ND2 and ND32 models that are the ones I usually use.

absolutely LOVE this filter. It stays on my zoom on my camera all the time!The handle to change filter level is easy, the filtering itself looks great and lets you get that perfect shot without switching filters. We took a trip this weekend and this filter never left the lens. If you take pictures outdoors, do yourself a favor and pick this up. No fiddling with any filters in your bag. Just turn dial it in and go.

bought the K&F Concept Variable Neutral Density ND2-ND400 Variable ND Filter (9 stops) with Rotating Ring to be able to use a fast ND with different densities. The packaging is very well done, solid and space-saving container. The glass filter feels light and the density increase/decrease ring is smooth. It does not have an end stop. To test it at its best, I tried it with three different lenses on a Nikon D750 camera (full frame): 20mm, 35mm and 85mm. - 20mm: in the photos taken with the filter, no particular loss of sharpness is noticed. introduces a slight warm dominant that can be easily resolved in post-production. As for the X-shape problem, it is quite marked using the filter beyond the marked ring. Using it instead within the marked marking the problem is not very present. See attached image.- 35mm: in the photos taken with the filter there is no particular loss of sharpness, it introduces a slight warm dominant that can be easily resolved in post-production. As for the X-shape problem, it is not as marked as in the previous one, but there is a vignetting especially when used to maximum effect. See attached image.- 85mm: in the photos taken with the filter there is no particular loss of sharpness, it introduces a slight warm dominant that can be easily resolved in post-production. As for the problem X-shape and vignetting are not relevant. See attached image. Therefore, optically the filter is well made and provides excellent results, however I would have preferred a start and stop with block in order to avoid possible errors. Furthermore, considering that K&F produces filters of other types but with a magnetic attachment, I think it could be a further plus for this filter. The quality/price ratio is correct on the basis of the services provided. I am attaching further photos of the packaging and two shots at the sea.

I got to try this filter for my Sigma 17-50, and the result is really amazing. The product looks great in its really great quality packaging and easy to carry in your bag.
The photographic performance is at a high level at a low price. I find the tongue very interesting, it allows you to have better grip during work.

I got to try this filter for my Sigma 17-50, and the result is truly amazing. The product looks great in its really high quality packaging and easy to carry in the bag. The photographic performance is of a high standard at an affordable price. I find the tongue very interesting, it allows you to have a better grip during work.

I have two of these variable ND filters with 55mm and 67mm filter threads. The filters make an absolutely high-quality impression, which is also supported by the packaging, in particular the storage box.
The filters have a scale on the aperture ring that starts at ND2 and ends at ND400. There are 8 stops in between. Unfortunately, the respective extension factor for each stop is not documented, so that the exposure time is difficult to calculate. Here, you have to get the best result by trying things out.

K&F Concept is synonymous with quality. I already had other filters of theirs, albeit quite old and with several years of service behind them. By virtue of my imminent photographic journey, I decided to opt for something new, always relying on them. I'll show you in detail what are, in my opinion, the pros and cons of their new product. First of all, the packaging is really excellent: the box is made of very sturdy cardboard, even impossible to fold, and then the magnetic opening is very pleasant. The filter is stored in a leatherette case with magnetic closure and not in plastic, which gives the product a finish that we can define as "premium". Inside, wrapped in a protective bag, is the filter. It is a fairly heavy piece, already to the touch it gives an excellent impression. The body is in aluminum, the glasses are of excellent finish. Very thin (and this is good because in this way any loss of sharpness is reduced), waterproof and scratch resistant. Very pleasant (and very useful!) the orange little thing that is used to vary the intensity of the filter itself: the only drawback is not having a limited stroke during rotation, but it is not a big problem, since the ND2 and ND400 are indicated right on the end of the filter itself. In any case, the filter has been constructed in such a way that, even when going beyond the limits, the annoying "X" shadow does not appear. For the moment I've only been able to try it in the city on a rather gloomy day, in the next few days I hope to integrate my review with other shots in the mountains. Who is the filter for? Definitely for those who love landscape photography or for those who have the desire to take long exposures in the city (remaining within the limits of 9 stops): of course, the product is not the cheapest on the market, but just try it for a while to understand which is worth every penny. I'm not a photography professional, but for my use it's just fine.

The handle to change the filter level is easy, the filtering itself looks great and enables perfect recording without changing the filter. We went on a trip this weekend and that filter never left the lens. If you are shooting outdoors, do yourself a favor and record this. No fiddling with filters in your pocket. Just dial in and off you go.

Top workmanship and very conveniently packaged

You can feel some vignette, in this filter it is from half to max. Everything else, like the picture quality, sharpness, fits the lense etc, is really good. It is'nt bad for the value of this amount money!