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.

Works very well. Diffusion looks pleasent and not super strong and my lens cover fits on top.

I am very impressed with the construction and performance of this filter and I wouldn't hesitate to buy this brand again. So now I have bought the brand again...

I don't know how to describe it, but this UV filter is shockingly clear. It's like it's not even there, but it is, and it looks beautiful too. If you've ever seen the glass that Apple stores use for their stores, it's like that (Apple uses a special glass for all of their stores and their HQ that is remarkably clear). This filter is like that. I haven't had it for long enough to see if it really holds up against scratches, bumps, water, etc., but just from initial feels, it seems like it does what it advertises.

So I think a lot of folks involved in video product are very familiar with the Tiffen Black Pro Mist filters. This is K&F's version of that filter. I will go into what I think about the filter but you can also judge for yourself in one of the pictures in this review where I show you the same image; the first without the filter then with the filter.

One of the results you get with a filter of this type is blooming of the highlights. This filter does quite a good job of that. Comparing the bloom to the Tiffen line I would say it falls between Tiffen's 1/2 and 1/4 strength with it being closer to the 1/4. The highlight fall of was strong but natural in my opinion. Keep in mind the light in the image fills the frame so you are seeing this particular effect of this filter at it's most extreme. You won't see that much blooming in a more natural setting. Take a look at the highlights on the camera. To me the K&F filter had a great effect on the highlight roll off which was very smooth.

The other effect you get with a black mist filter is the slightly reduced contrast and the slight softening of the shadows. To me I thought this filter did this quite well. If you look at the texture on the handle of the camera in the image you can see how it's just sort of softened that texture. Imagine shooting a person and you can imagine how much you would be able to smooth out the skin.

It also comes in a nice little screw together plastic case. Inside the case are these little rubber stopper than prevent the filter from sliding around in the case. I love the attention to detail here.

So compared to the Tiffen version of this lens at the size I got which was 82mm the K&F Black Mist is about $40 cheaper. I think you are getting a lot of value for your money here. I can't wait to try out this filter on some upcoming shoots.

I think K&F is making a move into higher end filters and if this filter is an example of the kind of quality they can produce, I can't wait to see what filter they release next.

I had used a popular UV filter before. It's not bad. Only under certain conditions would there be glare or aberration. For the most part it worked fine. But it still bugged me. So I ordered this K&F UV filter. WOW! What a difference! The glass is SO clear you can't tell it's in the housing! And that is how clear my photos became with it on! Definitely worth the price difference! All my filters are now K&F brand. The quality is outstanding!

As most K&F products, the build quality of this filter is quite nice. The threads are smooth, filter ring is powder coated and then optics... well, hard to say they're clear or anything since they're a diffusion/soft filter, but the picture quality is still quite good. More on that later.

The filter comes in a circular filter case that is one of the neatest filter cases I've seen! If they don't sell those as products yet, they honestly could! There are raised partial circles that allow you to place all sized filters in the case, unlike most with a foam cutout (which, admittedly offers more padding). It would be nice for the filter case to have a small sticker on it to indicate what is basically on the box--"NANO series 52mm MRC Black Diffusion 1/4" in my case.

The optics look like a clear glass with a bunch of small grey dirt specks. That is the intended design. The effect it creates is a soft diffuse glow; a bloom effect. The contrast is lowered when using this black diffusion filter and overall it looks like a similar effect to a soft filter. The sharpness at the point of focus isn't too affected though, so it can still be used in portraiture as well as in other creative photography. Light sources will bloom when looking through this filter. I find the 1/4 strength to still be quite useful while the 1/2 an 1 may be more niche.

The product came in beautiful packaging and with a handy case that can be used to keep several filter sizes. The filter looks nice and without any glare. I took several photos, which look wonderful. I haven’t explored many lighting situations yet, but since my main reason for the filter is to protect the lens, I am satisfied.