I really like this ND filter. Once the ring is attached to the filter, when I find myself in those situations that would benefit from an ND filter, I can just snap it on, rotate until I get the specs I want and take the shot. When it's not needed, I keep the ND filter in a protective case attached to the camera. The optical quality is first class, I have observed no issues with it. This is a very conveinient way to add ND filtering to your photography without the time consuming actions of screwing it on and off.

I have only been experimenting with this lens for a few days but it worked very well at the beach where I wanted to "smooth out" the water on a very brightly lit day. The photos came out well and the filter fit perfectly for me--I had no issues installing it or removing it (it didn't stick in place as some filters can). It is certainly an interesting filter for landscape photographers or those interested in refining their art.

Sometimes third party brands are hit or miss, but K&F Concept has never let me down. The fit is as expected, and the quality of materials is on par with the price point. What sets this particular lens apart is how rapidly you can change it out (literally in a second). The reason this is important is because if you're trying to capture something spontaneous, you don't always have the time to screw a new filter on, much-less take it off, so the interchangeability is great. That being said, the magnet isn't crazy strong, so I wouldn't advise using it for action shots if you're moving around a bunch, or maybe I need to snag their magnetic adapter ring. I haven't noticed any type of distortion or framing (like a vignette) around the border, so that's been nice as well, especially because that just adds to your workload in post. All around, I'd say it's reliable and does exactly what I needed - just make sure you understand the magnetic component before purchasing!

Initially, I did not like the fact that when I was trying to rotate to change stops, the whole body of the filter was rotating, but then I realized that there is a special lock of the filter when you place it on a magnet ring locking body of the filter and allow easy rotation of the adjustment ring.
The overall quality of the filter is superb. Great color and sharpness. No X pattern.

I received this for evaluation and thought that I would give it a try with a Fujifilm X-T3 mirrorless.

Generally, I run a UV filter on my lenses for a bit more protection from the elements (I like to shoot at the beach a lot and the salt air can easily leave a coating on the lens). But when I want to achieve slower shutter speeds to soften waves, I utilize a series of ND filters. This requires me to add a filter holder in front of the lens and then slide my ND filter of choice into the filter holder.

This set up makes the whole process so much easier. I can attach the included magnetic holder into my 18-55mm zoom lens. Then, when I want to attach the variable ND filter, I reach into my bag, pull this baby out and let the magnet attach it to the lens. It spins freely so that I can dial in the amount of ND that I want. No more fussing with multiple filters stacked in a filter holder. That makes me happy and leaves less room for error, more space in my camera bag, and less fumbling at the beach with the wind and sand blowing.

It is a tad pricey to me but the overall improvement of time, effort, and ease of use make up for the price.

Serves good for my Sony 16-35 F4. No image degradation as far as I can see even at 16mm

I love this filter. I can dial in how much/many stops of light reduction I want with just one filter vs carrying a bunch in my camera bag. Mounts to my nikon lense no problem and works well for long daytime exposures.

Over all build quality and design is very good but Having vignetting with 24mm lens, Best to use with higher focal length than 24mm

This is a nice filter. It works as expected without a color shift of X-Pattern.

The magnetic attachment is pretty cool. It allows easy changing of filters via a small magnetic ring. I don't currently own any of the other K&F magnetic filters, but I can see the value of the eco-system. I like that i can easily add or remove an ND filter without screwing/unscrewing. The magnet does seems a bit weak, so I'm curious to see if I'll run into any issues of the filter inadvertantly coming off. I'll report back if I have any concerns after road testing it more.

It rotates smoothly. I do wish it had a know like the 1/4 diffusion ND filter does. That was a brilliant design.

It comes in a sturdy clear plastic case.

For a variable ND filter, I'm happy with this.

This is a good adjustable neutral density filter with no problems I can see. It uses K&F's special coatings to help repel dust, water and fingerprints. This filter has a magnetic attachment system, there is a magnetic ring (with no glass in it) you screw onto your lens. Then whenever you want to use the ND filter you just pop it on and pull it off magnetically, making it easy to change. The system seems to work well, but it's the only one of their filters I have which features it. By rotating the filter you can go from ND2 to ND32, or 1-5 stops.

A lot of people wonder what this kind of filter is for, basically it lets you get some different effects when you are shooting in direct sunlight. For example, you can open the F-Stop of your lens all the way to get a shallow depth of field effect, then use the ND filter to darken the image back down so it is exposed right. Another common use is so you can shoot with longer shutter speeds in bright light. This will allow you to get that effect where moving water has a soft motion blur on it by setting a longer shutter speed and adjusting the exposure with the filter. It's also very handy for shooting video in bright light. Using a high F-stop and shutter speed for this can give you a video that has no motion blur and appears to stutter when the camera pans. The ND filter can allow you to shoot with longer exposures which will give motion blur and a smoother more cinematic look when panning.

So overall a very useful filter to have if you do videos or photos outdoors in bright sunlight.