I had previously used a common UV filter. It's not bad. Only under certain conditions would glare or aberration occur. For the most part it worked fine. But it still annoyed 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 case! And that's how clear my photos became with it! Definitely worth the price difference! All my filters are now K&F brand. The quality is excellent!

With this review I am referring to the product "K&F Concept Nano X-Series UV Filter 82mm Schott-Glas B270 28 Layers MC Super Slim", which I purchased in January 2023 and now after a few weeks I would like to share my experience.

Background:
As should already be generally known, UV filters are no longer bought for UV protection these days, since no damage from UV radiation is to be expected due to various lens coatings. The UV filters are therefore usually only used as lens protection to protect the front element of an expensive lens against dirt and damage. In the event of damage, it can simply be replaced.
I therefore primarily wanted protection for my Sigma 24-70mm 2.8 Art and my Sigma 35mm 1.2 Art, which have the same filter diameter.

Positive:
I could not detect any noticeable change in image quality in my tests. Both the sharpness in my test photos was the same as without a filter and I could not see any artefacts or disturbing light reflections. There are also several independent tests that compare the quality of UV filters - the K&F Nano-X does not show any major loss of quality, at least not in these either.
The ribbing on the outside of the filter is also very positive. This is (at least subjectively for me) actually helpful and creates more grip.
The box is also stable enough to safely take the filter with you to the place of use.

Neutral:
What is also often criticized with cheaper filters is the canting of the filter, which means that it can no longer be loosened. With my copy I could see differences between my lenses, but the filter always ran quite smoothly. At least I couldn't find any major problems. As you can hear in the attached video, it makes noises on my 35mm 1.2, but doesn't tilt at all.

Negative:
I didn't notice any points that would make me devalue the full number of points differently.

If this review and the attached pictures and videos were helpful, I would be happy to receive positive feedback ("helpful answer" button). If you have any questions, please leave them on the product page. I'll try to answer them there too!

I mainly use it to protect my lens from scratches and dirt.
It reduces the amount of ultraviolet light entering a camera.
Without this filter you will notice discolouration.
It effectively removes the appearance of blue tones bleeding in your photos.

I'm old school: I always put a UV filter on my lenses to protect the front element. If you want to know how valuable that is, just look at how far fewer lenses that have "just a little scratch" on the glass are being sold on FB Marketplace or eBay - in fact most people just would don't buy anything.

All in all, it's a no brainer for the price.

Being primarily a wildlife photographer, dust is more of an issue; I'd much rather dust off a cheap (similar) UV filter than possibly scratch the coatings on my expensive lens.

I didn't notice it with this lens, but most UV lenses tend to add the slightest, almost insignificant, blue cast to any image. Since I would process each shot I consider them decent and "worth it" in Lightroom anyway,

it's worth it.

I always get filters with non-slip design when it's available. It makes a big difference. I compared it to Hoya HD2. I shot this on Canon M50 with 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. The Hoya was visually as good as K&F except it was so static I had to return it. I also didn't like that it wasn't non-slip. The K&F is not static at all and very easy to clean. If there is no reflection, it looks like there is no glass in the ring. A bit like magic. It's very well done.
I use it on my Zeiss 50mm f/1.5 Sonnar T* ZM. There is no play and it fits perfectly. Very happy with the purchase.

Very good perfect sizes
Fast shipping and delivery

I'm usually against UV/haze filters due to concerns about their impact on image quality. However, I plan to use my Sigma 150-600 DG DN Sport (Sony E-mount) in fairly harsh conditions such as shorebird photography, surf photography and sports. So I gave in and bought this filter to protect the front element of the lens.
In view of the fact that this K&F filter would probably be classified in the "middle class" in terms of price, I wanted to test whether it actually had an effect on the image quality. The attached image of a $20 bill was taken in exactly the same circumstances - 600mm at ISO 100, tripod with no OS. As you can see from the screenshot taken in the comparison view of my image editing software, the image on the right (with filter) is significantly sharper and has higher contrast.
I am shocked! I fully expected to remove the filter if I wanted a better picture. Now I can leave it on 100% of the time and just wipe away any spills or dust without worrying about scratching the front panel. Strong recommendation!

I have a Black Mist Pro 1/8 filter that I use quite a bit, but wanted to try a 1/4 for a more pronounced "bloom" in conjunction with a dream sequence I was shooting. I've seen the K&F 1/4 Black Diffusion Filter for about 20% less than the cost of a Black Mist Pro so thought I'd give it a try. I have used K&F filters before and have always been happy with them, although some "professionals" perceive them as lower quality filters. I'm happy to say that the K&F 1/4 Black Diffuser performs every bit as well as the Black Mist Pro equivalent, producing exactly the effect I was looking for with no distortion or color cast. And if you consider the magnetic docking system, I would say that it's even better than the Black Mist Pro filter (this is the first magnetic filter I've used and I'm hooked). This filer is excellent value for money.

Screwing and unscrewing works easily. Used as a protection, even if there is disagreement about whether this makes sense or not. Since I don't want any accidental scratches on my lens, I put a UV filter on everything. Of course, that extra glass takes away some light, but it's very little. This is hardly noticeable in everyday photography. Am satisfied.

I use it on my Canon 24-70 f2.8 II and can't really tell the difference in terms of image quality. So that's the point of buying it and it does its job. The processing quality is good.