For ND filters (without gradient) the concept seems very conclusive to me. Incidentally, the additional ring can also be used to attach another lens to the magnetic connection. The magnetic force seems strong enough to me, it's actually not that easy to remove the filter without shaking the camera. You definitely don't have to be afraid that the filter will fall off at the most inopportune moment. The image quality does not suffer visibly from the filter, as far as I was able to judge tonight. Because dusk was already setting in, I was only able to achieve the same brightness relatively soon with an increased ISO (no tripod with me...), which of course led to losses, but these have nothing to do with the glass as such. the first pictures, that could still be shot with different exposure times did not show any significant losses even in the 100% view. However, there is a slight discoloration of the image, which turns purple with the filter. (Supplement a day later: in daylight and light snow, the picture with the filter was harmoniously balanced overall (trick: no strong contrasts...) and therefore significantly "warmer" than without the filter)

Review of "K&F Concept 67mm Magnetic Variable ND2-32 Filter (1-5 Stop) Set for Phone Lens Camera Mount Comaptible with iPhone 15 14 13 12 11 Series, Magnetic Neutral Density with Filter Holder" currently at £49.99:

I used this with my Samsung S20FE phone and it fit well even with case on. The filter is 67mm and fits over all the cameras on my phone easily. It has a nice smooth action for adjusting the ND level. It has a magnetic clip for the lens which is nice, but I would have liked a standard screw mount so other filters could be used.

It is quite expensive for what it is, especially as I can't attach other standard 67mm filters to it, but it does its job well so I can't really mark it down.

I bought the K&F magnetic CPL filter to mount on a Sony 18-105 lens. Although the filter is excellently made (even the magnet attaches well to the support ring), the main problem is that the lens cap (72mm diameter) does not attach to either the filter or the support ring, leaving the glasses unprotected. The return has begun.

The K&F Concept Magnetic Variable ND Filter offers a convenient way to control light for smartphone photography. While it has some strengths, it also comes with a few limitations.

Key Features:

Magnetic Convenience: The magnetic attachment system makes it quick and easy to apply and remove the filter.
Variable ND Range: The ND2-32 filter provides a decent range of light reduction for various shooting conditions.
Phone Compatibility: Designed to work with popular iPhone models, offering versatility for smartphone photographers.
Room for Improvement:

Image Quality Concerns: Some users have reported noticeable image quality issues, such as color shifts or vignetting, especially at the filter's extremes.
Filter Thickness: The filter adds bulk to your phone setup, which can be inconvenient for some users.

Overall:

The K&F Concept Magnetic Variable ND Filter is a decent option for smartphone photographers looking to experiment with light control. While the magnetic system is convenient, the potential image quality issues and added bulk prevent it from earning a full five-star rating. If you're willing to accept these limitations, the filter can be a useful tool for your mobile photography kit.

Good ND Filter for the 18-135mm Sony E-Mount Lens

The Magnetic Variable ND Filter is great for long exposer shots. The combination with the magnetic touch makes this absolutely flawless. would recommend.

In use on the Sony 20mm F1.8G and does exactly what it's supposed to do. Use it for videos in the sun

Since I discovered photography as a new hobby, I was looking for different filters. With this ND filter, you can turn day into night and thus make long exposures during the day and at dusk. Through the manual settings of the filter, msn can adjust this to the appropriate surroundings and lighting conditions. Magnetic Variable ND Filter, the installation is very fast, you won't miss a moment I totally recommend this filter.