I tested the K&F Concept filters on a Canon EOS 5D Mark III with a Canon lens.
I am very satisfied.

The filters are very well made. They are delivered well packaged. It is also practical that you get them right away in a well-padded bag and can thus store them well protected in the photo backpack. So the filters can also get no scratches and you always have the filters of one size together.

Also supplied is a cleaning brush.

The filters are absolutely accurate fit. This is not self-evident for filters of this price category.
I received the filters on a test basis which has no influence on my rating.

Original photos

Got this for my "nifty fifty" Canon 50mm 1.2 L lens on my Canon 5D Mark IV, and they're pretty solid.
You get three filters: (1) ND4 (2) CPL and (3) MCUV which are all pretty useful in different scenarios.
A huge plus for the included case, soft brush, and price point.
Overall, I would recommend this for any creator doing photography BOTH indoors or outdoors, and looking to significantly reduce reflectivity!

Yes... it works perfectly with Canon EOS M cameras. I own Canon EOS M10 and use this adapter most of the time with Canon 50mm 1.8 lens. It is amazing. The autofocus is accurate and fast enough. If you own a Canon EOS M camera, I recommend you this adapter because it is much cheaper than Canon original and there is actually no difference between them. Everything works as it should. I love this adaptor. The best purchase I've made for my camera.

This is a very nice high quality ND filter, as expected of K&F Concept. I'm using it with a Canon EOS 5D DSLR, and it is very fun to play with. I haven't used an ND filter like this before so I'm still learning, but you can definitely get some cool effects especially with moving water. The glass is high quality and the picture is sharp and clear. I have a couple of other K&F filters and this is just as nice to use as the others.

ordered the adapter to use a vintage Tamron mirror lens (5.6/350 mm) on my two Canon bodies EOS 5D mkIV and EOS 1Ds. Since both cameras are not listed in the compatibility list of the item description and one often hears (with other adapters) that the camera mirror can no longer move freely and therefore error messages or damage to the camera occur, I was curious whether that would also be the case my two cameras would work. It works out. The adapter is also seated without play, attaching and detaching is easy. It was clear to me beforehand that the focus and the time setting had to be made manually. Unfortunately, the invoice must first be requested from the seller, but it came within 24 hours as a PDF by email. However, it is an import invoice without deductible VAT and in the "worst case" the tax office will still have import sales tax when it is submitted. At the price of the adapter, however, that can probably be gotten over.

use the lens on my Canon 5d II full format camera - I am very satisfied with the imaging performance. Of course there is vignetting with an open aperture of 2.8 - but you hardly take pictures with it anyway. There are certainly better lenses - but you have to put down at least twice as much and therefore I can only recommend the lens to everyone who wants to use it from time to time. Anyone who needs a UWW professionally should take a look at the 11 or 15 mm from IRIX.

I bought it to mount Nikon F mount lenses on a Canon 5D Mark IV and III body and it fits perfectly with zero slack. As these are manual lenses, there is obviously no autofocus and the diaphragm is closed manually.

If they added a tab that closed and opened the diaphragm it would be 100% perfect.

With regard to the adapters from various manufacturers, which were often not exactly positive and the mostly positive voices about this product, I was very curious how the adapter would interact with my old lenses and the EOS 600 D from Canon.
I tested the adapter with old original Canon lenses:

1. Macro lens 35mm - Various plant motifs were photographed and the result was impressive. The objects to be photographed were also displayed on the camera's fold-out screen. In some cases, however, I had the impression that the light sensitivity setting was not reproduced faithfully on the screen. But after I experimented a bit with it, it worked satisfactorily.
2. Zoom lens 70 - 210 mm - The zoom lens can be focused without any problems even with the largest zoom factor (which has been criticized with many other adapters. The images in the viewfinder are displayed correctly on the camera screen. And the resulting images are flawless.

The The adapter itself can be easily attached to the camera and does not come loose when changing the lens. The two lenses used could also be attached to the adapter without any problems and are firmly in place.

Overall I am totally satisfied with the adapter. I do not know if a professional would do the same would see, but for me the resulting images are really good, especially when you consider how much money you save by using the old lenses.