It works as indicated in its specifications, a high-quality product for its price... recommended

I recently purchased the K&F Concept ND filter for my Sony FX3, and it has quickly become an essential part of my gear for video. From the moment I unboxed it, I was impressed by its sturdy build quality. While it’s slightly heavier than other filters, this added weight contributes to its durability, making it perfect for demanding shoots.

Mounting the filter was seamless, and I was pleased to find no vignetting issues, a common problem with ND filters. The filter performed exceptionally well in the bright, high-altitude conditions of the Peruvian mountains. It allowed me to shoot wide open in intense daylight without overexposing my footage. The color accuracy was spot-on, with no noticeable color cast, saving me time in post-production.

The metal frame and smooth threading make the filter easy to use, and the multi-resistant coating effectively reduces reflections and glare, which was particularly useful in harsh sunlight. It’s also easy to clean, which is a huge plus in dusty or wet environments.
In summary, the K&F Concept ND filter is a high-end accessory that pairs perfectly with the Sony FX3. Its excellent performance, durability, and flawless integration make it a worthwhile investment for any serious videographer, especially in challenging environments like the mountains.

Filter came in yesterday, I’ve played around with it in the house and this is going to make shooting 1.2 on sunny days so much easier. The glass is great, the build quality is high, I’m looking forward to trying out more K&F Concepts equipment. Highly recommend, I’ll make a video once it get warmer out.

I have this filer mounted on my Sony 24-70 2.8. The rings are made of metal and feel very sturdy in your hand.

I love being able to take photos mid-day and eliminate the harsh sun. It brings out the colors of the landscape and sky.

The filter is very clear and does not leave any of the artifacts that you sometimes get when using Circular Polarizing filters.

The included case is a nice bonus.

I love this filter. The quality feels and seems more than enough for what I need (recording social media content, travel videos, etc.).

The box is surprisingly one of the most premium experiences I have ever gotten unboxing something.

And I have bought over 20,000 euros on video and photo equipment, so yeah, pretty cool box.

The only thing (I'm splitting hairs here) is that I wish the golden handles would have been way less pronounced and subtle. I would also have loved to have a lens cap for it. But other than that, I just loved it.

It makes my videos way, way better. I'm using it with my Panasonic S9, with an 18-40mm.

I would recommend this to anyone wanting to improve their videos instantly, if they are recording outdoors.

You can still record indoors, assuming you have sufficient light.

The K&F Concept filter comes in very elaborate packaging along with a pouch and a vacuum-sealed cleaning cloth. The packaging also lists the importer's address in Frankfurt, as well as the manufacturer's address in China. The origin is "Made in China."

The filter itself, as I've come to expect from K&F filters, is extremely well made. I bought the 49mm filter. I was very surprised when I unpacked the filter. It's a 67mm filter with a 67mm to 49mm adapter.
The filter screws on easily and is also extremely easy to move for the polarizing filter function.

The case is also well made. It has a strap inside the case to easily remove the filter from the case by pulling on the strap. The case closes magnetically.

I've already taken my first steps with the filter, but so far I'm still in the practice phase.

Conclusion:
The filter is well-made and easy to handle. I give it a full 5 stars.

After trying countless filters, this is the one that has given me the best results. I haven't noticed any color shifts or loss of sharpness, unlike what I've noticed with other well-known brands. I'd also add that I've tried many different models.
The polarizing filter included in this ND filter is indispensable for me. When the ND filter creates a bit of a vignette at wide angles, I can correct it with the polarizer. Plus, I have complete control over reflections. The build quality is very robust, and it looks great.

K&F has now earned a fairly good reputation among photographers, not least due to the very attractive price-performance ratio that K&F products generally offer.
And now, K&F seems to be reaching for the stars and, with the Concept Nano-X PRO series, wants to reach the segment of customers who value high-quality products and are willing to pay accordingly.
I tried to find out whether this will succeed using the Nano-X PRO Variable ND Filter.

With the Concept Nano-X PRO series, K&F, as already mentioned, wants to reach pro users, and these users typically rely on filters from well-known brands and are willing to pay accordingly.
And I've already had the opportunity to experience extensively in the past that K&F is quite capable of producing good filters. Of course, a little compromise had to be shown here and there, but that was quite bearable, especially considering that the filters were previously more in the affordable segment. Things are completely different with the Nano-X PRO series. If K&F wants to live up to the price, they have to deliver unconditionally.
And yes, they do… starting with the materials, the workmanship, and even the quality of the coating, with the Nano-X PRO series, K&F no longer makes any compromises and demonstrates what is technically possible.
Gone are the days of stiff threads or seized filters! The ultra-precisely manufactured brass mounts of the Nano-X Pro series run as smoothly as butter and convey the feel of a Peter McKinnon Polar Pro filter

Beautiful lens and great customer service from K&F

K&F is my go to company for all this stuff. These work well they are real glass. Quality is awesom.