K&F is really making some fantastic filters as of late. The build quality on these are excellent. Precision machined brass rings that are thin enough not to interfere with the image but strong enough to protect your glass. They screw on very smoothly and the brass will prevent stripping and cross threading.

The optical quality of the glass is excellent. There is no distortion whatsoever and the mist filter gives your images a very subtle dreamy quality. Something really impossible to do in Photoshop or with digital editing in my opinion. You get the realism and quality of an actual optical effect, and these look absolutely beautiful. Some people may disagree but I always prefer doing as much as you can in camera to eliminate the need for post processing. And of course for video it’s definitely a timesaver. Applying this subtle mist effect digitally in video is very processor intensive.

This is a nice little way to soften the features for portraits and I decided to take a portrait of this little fellow. You can really see the difference around the eyes that the filter makes in addition to the fact that it was really bright and this filter helped soften the shadows.

This is a 1/4 Mist so the effect is very subtle. Don’t be confused by the name black diffusion. This filter will lighten your images by reducing contrast and softening highlights. It actually lightens up the image a bit but in a way that doesn’t create blurriness. That’s the beauty of genuine optical filters rather than digital post processing effects.

This is comparable to my German filters that I paid a lot more money for in the past.

Lenses of modern digital cameras are increasingly being trimmed for sharpness and imaging performance, which is of course good on the one hand, but in turn also brings with it a dilemma, namely that subjects often appear harsh and contrasting and images, somehow lack a certain charm.
To defuse this modern “look” a bit, to make motifs a bit softer, highlights diffuse and a bit softer, that's what effect filters like the Nano-K Black Diffusion from K&F Concept are for and are particularly popular with cinegraphs.
But photographers also benefit from such filters, as portraits, for example, get a pleasant, somewhat dreamy look without losing too much sharpness.
The diffusion effect is best when a light source, such as a window or lamp, is in the field of view.

In the beginning, you will have to experiment a bit to find the optimal filter strength for the desired look.
In my opinion, the K&F Nano-K Black Diffusion ¼, which I tried out, is ideal for gaining initial experience, as the filter strength of ¼ already makes the diffusion effect very effective, but still maintains sufficient sharpness and contrast.

Both haptically and qualitatively, there is nothing wrong with the K&F Black Diffusion. The filter is very well made and has a flat profile to avoid vignetting. The thread is cleanly worked and runs smoothly.
I couldn't notice any noticeable color shifts or vignetting.

Tip: I always buy filters according to the largest lens diameter in my inventory and adjust the filter, using step-up rings, to the lenses on which I want to use the filter right now.
This has the advantage that you only need to buy filters once and even though large filters are of course a bit more expensive, like small ones, it's worth the bottom line, as step-up rings don't cost much. It may also be worthwhile to buy a complete set of such adapter rings, with different diameters.

The &F Concept Nano-K Series Black-Mist 1/4 filter arrived quickly.
It is always well stored in an appropriate case.
Three separately packaged wipes are also included.
The workmanship looks reasonable.

The filter fits and is easy to install.

The effect is subtle but visible and enhances one or the other image.

I'm satisfied.

A filter in a simple plastic box and 3 cleaning cloths are included.
Using the filter is easy — the results are okay.
I had previously tested a 1 filter, which I found too strong. The 1/4 Promist filter is more discreet and pleasant.

The Black-Mist filter makes the image a bit softer and more “flowing”. This is particularly noticeable when it comes to bokeh (background blur) and incidence of light. This makes the bokeh appear a bit softer.

However, this effect is rather subtle. The 1/4 filter is not excessively strong. Especially in focus, the sharpness remains quite high, but that's not a bad thing either.

There is nothing wrong with the K&F filter in terms of quality. The filter does what it should and is good to use as a creative tool.

Well made filter. I got the 1/4 filter in 72mm size. Great for portraits....gives a softer edge and a slight glow on the highlights.

This is subjective, but I wouldn't go any stronger on the filter strength, and in fact, you might want to consider the 1/8 strength filter. Too strong a filter like this makes your photos were taken at an '80s Glamor Shot booth at the mall...

This has become my favorite filter to use! I photograph a lot of athletes, and often put lights behind them, and with this filter, I'm able to make those lights bloom out, instead of being too sharp and harsh. Big fan!! Great quality and feel too - will be getting more of these in other filter sizes.

I have a few black mist type diffusers, including the more expensive K&F Nano-X, and even more expensive Tiffen. I bought this Nano-K series version half expecting to return it but thought it worth testing out given the much lower cost. Construction-wise it is as solid and well made as the Nano-X using the same finely machined “aircraft grade” aluminum. Screw thread is precise and smooth. K&F give very little useful information about the the actual differences between their filter series, except that the Nano-K is meant to be “basic level” compared to the supposedly more professional Nano-X and Nano-X Pro series. If you read the manufacturer’s small print, they are all made from optical grade glass from Japan, have advanced multi-coating and resistant to moisture and mold. So what about the effects performance? Again, I was prepared for disappointment. All brands of this type of black diffusion filter have subtle differences, as is well covered by numerous YouTube videos. The Tiffen for example tends to give slightly less intense diffusion for a given rating (i.e., 1/4 vs. 1/8 etc.) than the Nano-X, but both are equally good a preserving the blacks and fine detail in the mids, which is why we like them. When compared to the Nano-X, I can see no visible difference whatsoever in the image produced by the Nano-K. This was tested on a Canon C100 Mk-2 with a variety of lenses and conditions. For this reason, my advice would be, given the choice between the Nano-X and Nano-K, without hesitation get the latter. A side note: the Nano-K series appears to have been originally marketed in Germany, evident from Google searches and the small print on the packaging, i.e., GmBH, as place of origin. My conspiracy theory is that these were initially targeted for a European demographic and price expectations. Anyway, the bottom line is that here in Canada/USA they are a phenomenal bargain and not to be missed while available.

Modern cameras with good optics produce crisp, sharp photos. You can see every detail here.
No crease, scar, or impurity remains hidden here.

Especially when you want to photograph portraits, this wealth of detail is not always wanted. Unless you want to highlight the wrinkles, etc. as an artistic device.

But if you simply want to create beautiful portraits, this filter can be used. It mitigates precisely these weaknesses, if you can say so, and produces wonderfully soft - though not blurry - results. The contrast is also reduced, which simply creates more beautiful photos from hard and cold light.

The filter I have has a strength of 1/4 and is therefore the second weakest. All the effects mentioned above are therefore present, but not so strong that it appears artificial and perhaps even kittish.

Sure, you can now say that such effects can also be done in post-processing, but this filter saves you a lot of work and has a more analog workflow that I personally really like.

In any case, the filter has already proven itself and is more than worth its - low - price. Especially since there are three good cleaning cloths as a nice bonus.

I can't identify any negative points, so I can give it the full five stars here.

I received the K&F Concept Nano-K series Black-Mist 1/4 filter free of charge for testing. The product was delivered quickly and was securely packaged in a standard retail box.
The filter is well padded in a sturdy plastic box. 3 shrink-wrapped cleaning cloths are included. The filter makes a good visual impression and delivers the promised results in the image. The thread is smooth and fits perfectly. In today's fully digital age, filters have gone out of fashion, as most effects can be added digitally afterwards. For analog photographers or people who don't like to digitally edit images, this filter is highly recommended. The filter strength ¼ results in rather unobtrusive subtle results. The manufacturer describes the filter effect very appropriately. With appropriate step-up adapters, the filter can also be used on smaller lenses. Good filter. Nice effect. Good workmanship Reasonable value for money. 5 stars