This is a TEST REVIEW for the item sold on Amazon with the description: K&F Concept Nano-K Magnetic Filter, CPL Circular Polarizing Filter with Nano Coating for 77mm Lens (Cleaning Cloth Included). This is a CPL filter (polarized light is controlled by rotation around its axis) that is very comfortable to use thanks to its two-part threaded anchor ring and the filter with magnetic outer ring. The threaded ring is installed and then it can be removed with a simple grip and pull on its contour (which has a ribbed texture for a better grip) and to fix it again, then present it on the ring and position it until you find the magnetic pull and its anchor in a well-adjusted position. In terms of performance, they stand out outdoors in good sunlight (indoors and artificial light is imperceptible) and outdoors very shady. Therefore, it is usually useful when shooting landscapes, especially in areas where an area of sky or clouds appears, or where light is reflected in rivers, springs, lakes, etc... or in reflections with a metallic effect. Depending on the orientation in which the ring is rotated, the image becomes slightly darker or brighter, attenuating the sunlight and taking on a greater or lower color saturation (when rotated on the magnetic system it sounds a little like a rubbing squeak, but as is usually used in photo and video recordings, the position is first sought and then the recording is activated, as this does not affect the tone of the recordings). I made an edited video with some image changes in the same shots, with the CPL polarization ring only partially rotated. The images appear with a higher hue but less luminous, which is why it is advisable to adjust the gain of the light meter a little, because if we rotate the ring when we are in manual mode or in the preferred aperture or speed control modes with respect to it, the recording speeds and apertures vary respectively, and personally I like images that are a little more vivid both in colors and brightness, but without annoying reflections. Due to its very good price/quality ratio and its ease of installation and replacement with filters from the same “Magnetic Adapter Ring” magnetic attachment ring system, its thin “Slim” mount that prevents vignetting on square lenses, its good presentation in a protective box and the special cleaning cloth included in the set, my rating for this K&F Concept filter is: “5 STARS” = [* * * * * *]. I hope you find this review helpful, Best regards. The disadvantage that I forgot and that I noticed later is that on CANON lenses with the EF series front caps, they do not attach with the filter installed or with the filter removed, since the filter is a narrow format (SLIM), the retaining tabs of the lens front cover do not engage with the profile of the filter or its support ring. To be able to put the cap on, you must also remove the threaded ring and store the set in the box.

Had seen some reviews on YouTube. When unpacked, it looked a bit cheap. But functionally better than I thought. The amazing quality with the 12Mpix camera and lens isn't too bad either. The construction is simple and feels cheap, but in my first picture it doesn't compromise the functionality and quality of the image on the screen. Haven't gotten the videos and photos on the PC yet. It also works with a rechargeable/mobile battery bank so nice and versatile and a mobile setup is possible.
The magnification with a sharp image is so good in terms of resolution in combination with the lighting that, in addition to electronics, it is also suitable for biological and photomedical applications such as viewing and enlarging the skin. That surprised me a bit. The camera and lens can also be removed from the stand and can therefore be carried on the move. The image is more stable under a stand than in the hand, but solutions to this can also be devised with some Macguy pens.
Software is basic but the instructions in the manual are easy to follow.
The wiring was designed to be a bit awkward, but I understand the reason and functionality behind it. I think this could have been partially integrated with fewer cable hassles and vulnerable ports. But from a simplistic cheap architectural side I understand the logic.
I sometimes find the light too white. A warm white color would also have been nice to see true colors. The white light is sometimes overexposed. The light is strong, but it can be adjusted and the microscope ranking is dimmable.
I find all kinds of settings icons on the screen very annoying. It distracts from the picture. I haven't found a settings function to turn this off.
Points for improvement:
Actually pretty good for the price.

1. Mobile crafting with fewer cords
2. Warm light option for true-to-life images.
3. More megapixels. The more details are visible. The lens magnification is good but can optionally be a notch higher as a mountable accessory.
4. Software option to hide settings and clock and date from the screen.
5. Slightly more robust wheel. so I can make better micro adjustments with the focus/focus point of the lens. Things are going a little rough now. I believe this is due to the coarser plastic grooves. Perhaps a metal rail is a better option.
6. visible buttons on the screen. The function is plastic, so black on black, and therefore no contrast. If it was colored white, it was more visible. More contrast.

First impressions: - good looking - fine workmanship - matte interior finish (light doesn't jump in) - smooth conformance to camera body - smooth shift rotating One ring - comes in an unsealed hard case and nothing else on it - out of the box with any vintage Nikon mount usable lenses - orange ring gives the looks to the whole camera setup - the adapter fits harder on the lenses (needs to be attached) - focus is based more on the depth of field (FOD) difference in the picture frame - it works more like zone focusing and precession focus zones are heavy to reach - metal mount on lens side and (I think it's still a metal) black plastic which looks nice, camera charcoal mount (it's passive adapter and therefore no electrical communication between lens and camera) - light doesn't get through the adapter into the Barrel (sealed fit) - it should come with end caps to the adapter to keep dust out when not in use - for the money I paid I like experimenting with my old lenses on the Sony mirrorless body

For a lens that's so cheap, I'm genuinely surprised at how good it is. I think it's better than Nikon's own lenses. I use it for light colors mostly, and fur, two things you need a good lens to capture with minimal difficulty. It works amazingly in all lighting conditions, the autofocus is flawless and the image quality when paired with my D7000 is unfathomable.

this is a cheap bargain, good pic quality and nearly no colorcast. The ring is very thin so suits wide lenses.

Well made, good quality, fits my Fuji perfectly. Be sure to choose the version with the aperture ring! There is no autofocus, as the adapter enables a purely mechanical connection, but manual focus gives the photographer completely different options as long as the images are not moving. I use it with Nikon's cheap Nifty Fifty (AF Nikkor 50mm 1:1.8 D) for still images, portraits etc. The Fuji XF 18-55 f2.8-4 RLMOIS for everything else that's more moving. A good, cheap, compact and not heavy team for excellent pictures. It is important to set "Capture without a lens" to 'On' in the menu under 'Wrench' / 'Key wheel settings'. Since the adapter is purely mechanical, the Nikon does not recognize the lens. Once set like this, both the Fuji lenses and those connected with an adapter ring will work. Top!

I like the selfie ring light, only issue max brightness is not that bright but it is good.Also, the buttons to control the light need to be closer to base rather than hanging in the middle of power cable.

It is a simple ring light that meets the purpose. The quality is ordinary but still recommend given the good price.