I tested the K&F Concept Nano-X PRO series polarizer 67mm with the Sony A7RII on a Sony SEL-20F18G. I use polarizing filters for 99% in landscape photography. Since the effect is virtually impossible to simulate in post-processing, a polarizing filter, in addition to grey filters, is one of the only material filters that I regularly use.

The K & F is one of the slim filters. This can prevent vignetting in an extremely wide angle, but the slim frame makes handling much more difficult. Due to the design, this is the case with almost all manufacturers. After all, the filter has a threaded socket at the front, so that several filters can be screwed one behind the other. Depending on the type, the lens hood and lens cap can also be fitted. The filter comes in a high-quality, sturdy bag with magnetic closure. As a little gimmick, the manufacturer also includes a microfiber cloth for cleaning.

The thread can be unscrewed cleanly. The rotating frame runs smoothly and smoothly. The slim design makes handling sometimes very difficult. On the one hand, you have to be careful not to screw the filter too hard onto the lens, otherwise loosening it by hand will be difficult. On the other hand, when turning the filter counterclockwise, there is a risk of unintentionally loosening the filter if it is not screwed on firmly enough. With the lens hood attached, operation is also no longer possible.

The glasses come from the Japanese house Asahi Glass and appear to have a high-quality finish. I was unable to detect any loss of sharpness even at extreme magnification. I was able to notice a slight color deviation into reddish. However, this is really barely noticeable. Since my used lens is not susceptible to lensflares, I was happy that there was no deterioration with the filter on. The filter absorbs almost exactly one f-stop of light, which is a very good value. The filter effect is good, but I honestly didn't expect anything else in this price range.

In my attached pictures, you can see the result with strong backlight, both with and without filters. I couldn't find any differences in quality or lensflares here. You can easily see the filter effect on the leaves on the other two pictures. Here, sunlight falls on the shrubs at an angle of about 90 degrees. The polarization effect is clear. The white balance was set manually to daylight for all shots. The only very slight color shift is barely visible here.

So far, I haven't had K&F Concept on my screen in this price range. The results of the filter are first-class and do not reduce the quality of my high-quality lenses. Unfortunately, you have to live with the somewhat difficult handling of this design, and K&F is not reinventing the wheel here either. However, I give the full five stars for optical performance.