Great filter with nice features at a decent price. About 3mm thick. Screws on fine. Hard case.

In the pictures, the first image is with the filter on, the second one is without the filter. Shot with the Nikon 50mm f/1.4 lens at f/1.8. The main difference is in the highlights area. Note how there is loss of contrast and a gentle glow effect around the candle lights and around the stronger highlights. Also, there is a very subtle, dream-like haze in the image, the image sort of feels a little bit warmer.

I can definitely see how this filter will have its place in my camera bag.

Quality-wise, the filter is very nicely made. The storage case is hugely oversized. Looks like the same case size is used for all filter sizes. This is suboptimal for the consumer, since there is no reason why I need to find space for the huge case for a small filter.

The retail box is presentable, and projects quality. The whole package would make a nice gift.

I am usually against UV/haze filters as I am concerned about their effect on image quality. However, I plan to use my Sigma 150-600 DG DN Sport (Sony E-Mount) in pretty harsh conditions such as coastal bird photography, surf photography, and sports. So, I caved and purchased this filter to provide protection for the lens front element.
However, given that this K&F filter would probably be considered "mid-tier" in terms of price, I wanted to test if it in fact had any effect on image quality. The attached image of a $20 dollar bill was taken under the same exact circumstances - 600mm at ISO 100, tripod with OS off. As you can see from the screenshot taken in the compare view of my photo editing software, the image on the right (with filter) is clearly sharper with better contrast.
I'm shocked! I had fully expected to remove the filter when I wanted a better image. Now I can leave it on 100% of the time, and easily wipe off any splashes or dust without worrying about scratching the front element. Strong recommend!

Both lenses are Sigma lenses with 2 different brands of UV filters on them. The lens on the left is my 150-500mm with a filter made by another brand. The right is my 150-600mm lens with the K&F filter. The lens on the left looks a little hazy, while the K&F filter does not.

Does not decrease image quality that I can tell. You can feel that it is weather sealed.

Comes in a plastic case

Love the quality and size. Item was packed like a piece of fine jewelry. Highly recommended.

I always get filters w/ non-slip design when it's available. It makes a huge difference. I compared it w/ Hoya HD2. I shot these w/ Canon M50 w/ Nikon 35-70mm f/2.8 AF ZOOM-NIKKOR.
1) No filter. 2) K&F. 3) Hoya HD2.
Sure, it's not a great test but I can't tell any difference between all 3 of them. The Hoya was optically as good as K&F except it was very staticky that I had to return it. I didn't like it's not non-slip either. The K&F is not staticky at all and very easy to clean. When there's no reflection, it looks like there's no glass inside the ring. Kind of like magic. It's very well made.
I use it on my Zeiss 50mm f/1.5 Sonnar T* ZM. There's no play and it fits perfectly. Very happy about the purchase.

Includes: case, and filter.
Tested with my nikon kit lens. (see my sample photos)
Each Top photo was taken on a tripod with a 10 second timer.
Each Bottom photo, the black mist pro filter was added.
This really does work as the name suggests!
Side by side you can see the colors and focus in the original without filter.
Then after applying the filter to the front of the lens,
you get a black mist. This calms down the color saturation and the sharpness.
Just a small amount.

The case.
Top twists off from the bottom and is made of a smoked plastic. The edges have a nice groove set.
Makes opening and closing easy. Branding on top.
The bottom is made of the same plastic and has the same grooves on the side.
The highlight is the 2 gray silicone pads that are glued down inside.
(These grooves will hold you filter) You could also use with smaller and larger filters.
That's a plus.

The filter.
Is slim line and made of aluminum.
Sides have really nice grooves, makes using the filter very smooth.
Great glass. Actually scratch resistant.
Took out my keys and hey no scratches. Thumbs up.
Waterproof.
Filter weighs only .5 ounces. Both the case and filter weight 2.7 ounces.

Overall very pleased with the filter.
Great quality.
I picked up the 52mm version.
Used 2 of my kit lens and no issues. Very smooth to install and remove from lens.
Easy to clean. Should last a very long time.

I prefer to shoot with filters verse going into software and spending extra time to get a similar effect.
Hope this was helpful.

Just got a new lens, needed a 77mm filter to protect it. I'm not going to sit and tell you this glass is better than some other glass. I just got it, and I'm not an optics expert.
But, I will tell you the packaging was beautiful, the filter case- one of the nicest I've ever seen. It is circular- and holds multiple size filters with grooves in an internal bracket. So much nicer than the big clunky square filter boxes I've got from other brands.
But- the killer was the filter being so thin- and that it has 2 areas that are gnarled, for you to grab it- while the rest is smooth- a really nice feature.
Seems right at home on my Canon RF24-105/4 L IS USM.
Didn't notice any difference in speed of focus- or aberration- but, again- I'm not a lab.
I'm pretty happy with this brand. Didn't expect to be

I purchased this for a camera that I seldom use. It still is a valuable collectors item that I want to keep in excellent condition and that means I needed to protect the lens. I only have filters with the Zeiss "T" coating constructed of German Schott glass on the cameras I use frequently, because I consider them the best multicoated filters that I can afford but, I cannot spend that kind of money for a camera I use infrequently.
Any camera that is threaded to accept a filter deserves the protection that comes with a mounted filter in front of the actual camera lens. I would rather risk damage to the AR coating on a filter that can be easily replaced than risk damaging the actual lens on any of my cameras from cleaning, and exposure to airborne dust or chemicals.
This brand of filter came carefully packed and the filter holder included with the filter is well designed and provides excellent protection for the filter when it is not on the camera lens because I am using a different type of filter. This filter has multiple AR coatings on both sides of the filter and after comparing the results of identical pictures with the same camera using this filter and one of my prized and now unaffordable Zeiss "T" filters I can say that I can see no difference in the results. I am sure an optical lab could document some differences, but in the real world, I can see no differences when comparing the test pictures I captured through this filter and the Zeiss filters I have used.
This design works so well, I will slowly replace the older non Zeiss filters I have on my older lenses and cameras with these newer designs.

So far so good. It adds the right amount of haze for portraits to make it's stylistic. It doesn't add too much in my opinion, and the picture is still pretty sharp.