K&F makes quality photographic gear at a modest price, I have been happy with their products in the past and this filter is no different. It comes in a sturdy box and a plastic lens holder along with three lens cleaning cloth in hermetically sealed envelopes.
It easily screwed on to my beat-up Sony 24-105 G lens, it also stacked on to the UV filter. It feels well machined and has a knurled edge for an easy grip.
The effect is pleasant and slightly painterly. I don't feel comfortable uploading headshots of people, but it softens the highlights in portraits in a nice subtle way especially if there is strong rim light. 1/8th is a very subtle.
I would like to add that most of the time a blooming light source looks good, however if you have a subject in front of the bloom it can obscure the subject. You can see this a bit in the my photo with the house light behind the rock. The bloom is cool looking however if that had been a model it would blocked her.
I often add a glow or the variation called the Orton Effect in post. This black diffusion filter is cleaner in that it only affects the highlights. I tried the filter on a sunset shot and it had no change at all, may have to go to a 1/2 or a full diffusion to see any change.

Diffusion filters like this come in "black" and "white." The white ones I like to call "bottom up" diffusors. They increase the brightness of the shadows as they diffuse.

A black diffuser is a "top down" diffuser, taking the highlights down slightly while softening the image.

Fits my Canon L-series lenses perfectly, and as a diffusion effect, gives nice image quality at a good price. In fact, where some types of filters are worth paying the premium, a diffusion filter is a place to save a little cash when you can. Since the effect itself essentially degrades the image to get a creative effect, so long as the creative effect looks good, you're getting your money's worth.

Five stars.

The threads are nice and smooth and the optics of the filter is quality. The effect might seem subtle to most, but it does give portraits a little something extra, and also work nicely for video. All of the lens wipes were a nice added bonus!

K&F Concept 77mm Black Diffusion 1/8 Filter, Mist Dreamy Cinematic Effec Filter for Video/Vlog/Portrait Photography K-Series

This is a 1/8 stop black diffusion filter that lowers contrast and makes highlights glow. It’s not quite a soft focus filter, it does give the overall image a softer, dreamier and glowey effect. K&F filters are very well made and very well engineered. I have been using several of their filters recently and I rate them among some of the best in the business. These black diffusion effects are pleasing and subtle at least with the 1/4 and 1/8 stop filters. The effect gets more extreme with the 1/2 and 1 stop models. These are great for wedding, glamor and portraits, or anything you want to have a soft diffused glow to the image. Equally effective for video and photos. A fun effect to play with for added drama and vibe. Works best with scenes with lots of background highlights, or very backlit scenes. Modern lenses and sensors are so sharp that sometimes you just want a softer vibe, this is a good tool in the tool box for an instant dreamy and dramatic quality.

I have tried, and own, different grades of black diffusion filter. I think for its subtle effect, this 1/8 filter is my favorite. The smooth look, and highlight diffusion that you get with these filters, is either an acquired taste, or a specific characteristic that you're looking for in your shots. I personally don't use them all the time, but it is nice to bloom the highlights in certain scenarios. The 1/8 filter is very subtle in the daylight, but I found excels at night. You can of course, use it with decent effect during the usual golden hours, as the intensity of the highlights then, may be more visibly changed by this filter, photographically. In the daytime, with the sun right above you, it's hard to notice much of a difference. For video, it does an interesting effect, and may be something that you can apply to specific scenes, or just to unsharpened some of the digitized look from most cameras. Quality of the filter is very nice, made of good materials, and with nice coatings. It comes well packaged, in your standard plastic case, as well as included sealed microfibre cloths. It is affordably priced, and performs very nicely, for that price range. It doesn't in any way appear cheap to me, and like mentioned before, I do like the subtlety of this gradient. It's certainly good for the camera bag, and would be interesting to try with some golden hour portraiture. For video, I'd say it's limited to dreamlike sequences, and better suited for golden hour, and night time. All in all, I'm very pleased, and if you're looking for a 1/8 black diffusion filter, this one is a good choice.

I have the 1/4 filter as well and I feel the that is just slightly stronger than this. They are both subtle and soft, with this being ever so slight. this is no sledge hammer, but a delicate mist. A very soft diffusion on light sources and specular highlights. A softness to the skin. this is a much, much lighter effect than the old, high end French silk stocking over the lens. ever so slightly dreamy, a light glow without being overkill. I have not compared to pricier brands, but I am quite happy with this. I don't imagine that I will be bringing it out for much more than portraiture, I intend to experiment to see what it can bring to my other photography work.

Beautifully packaged and secure, with the added bonus of 3 microfiber cleaning cloths, this is quite the bargain if you are in the market for such a filter, but if you want to have a noticeable effect you might go 1/4 or stronger.

Probably should have got the stronger filter effect. Nice filter though.

gives you that beautiful haze and glare from natural and or studio lighting

Crystal clear glass giving my pocket 6k pro and sigma lens combo the closet look to the Arri without the hefty cost! Love it, wish I had invested in these sooner.

An excellent diffusion filter. It looks more like a standard diffusion than a black diffusion. So you get the highlights to bloom but retain contrast.
And at 1/8th its not to strong for most situations.
Absolutely love these. K&F have another winner on their hands.