For the price a top product.

... with color photography, the polarizing filter unfortunately produces a color cast for me, so I had to send the filter back. Bought for practical reasons because of the 2-in-1 function, but now separate fitter for polar and grayscale function have to be found. I didn't use/test autofocus.

The filter is very suitable for reducing the light sensitivity of the camera and thus facilitating long-term shots (e.g. of roads). The cross shadows mentioned in some reviews I can not perceive in any of the settings of the filter. I use the filter with a 50mm lens on a Nikon D5100. Water and glass reflections can be easily removed by simply turning the filter.

only tried it a few times but very impressed so far

I was given this filter by K&F concept to review, but this is my honest review based on using it for a few shoots of both photography and videography. The filter comes in a really nice plastic protective case, also included is a cleaning cloth in a pouch. The cardboard box itself is sturdy with a magnetic opening. I asked for the 77mm filter to fit my biggest lens and got some step up rings so I can use this on all my lenses and by stepping up you wont get vignetting. The filter itself feels very good quality and well built, the exposure adjustment ring allows you to choose between five stops, it feels like a fluid video head and will not move on its own. I didn't witness any colour shift, or any photo or video issues using this filter, also there was no sign of the black X some filters show when the two optics cross at their maximum point. I would definitely recommend this variable ND filter, its at a very good price point and by using step up ring for around £10 you can have this one filter work on all your lenses, that is a lot cheaper than a few sets of ND filters when your lenses have different sized filter threads. Using this on video at either 25 or 30 fps using shutter speeds of 50/1 or 60/1 this filter easily cut down the light to stop my footage being over exposed. I have added a review on YouTube and video demo, you can find this by searching youtube for this product description.

Great filter I didn't find a color cast used on Canon L-series lenses, no problems, the only thing I found is that the rings are a bit tight but will probably wear off over time.

At first, I wasn't quite sure about the price, but that quickly changed when I started using them. I had tried the K&F in the next higher price range, but found that I could not justify it for my pure amateur photography.
If you want good quality at a reasonable price, these are worth a look. If you're more professional/business-minded, you don't need reviews created by amateurs like me on Amazon.
All in all, I highly recommend these filters - I'm lucky that I only need three thread sizes for my Canon L-series lenses, otherwise it could be very expensive!

A super versatile and cheap nd+ polarizing filter, fantastic to use for videos, shame for the lack of front thread.

Very fast delivery, the filter comes in a high quality packaging. Was a gift for my sister and she is very happy with it! Therefore top purchase, I can only recommend! :-)

I have always been a fan of K&F after buying their tripod, so I was pretty sure about the quality of ND. This is 1of 3 NDs I have purchased for my crew, and I should say this is amazing. I would start with the build quality, and it's pretty sturdy, the casing is aluminum and lightweight. Coming to the colors, I didn't see any difference in colors with ND on at Min and ND off. Also, the cutting down of light from ND 2 to ND 32 is so accurate for an ND(measured with exposure meter).