K&F Concept HD Putter 49 мм ND2-ND400 (9 ступеней) переменный нейтральный фильтр, регулируемый водостойкий / устойчивый к царапинам для объектива камеры (Nano-X II)

Very well made high quality filter from a brand I have used before. It's slim, waterproof and has an anti scratch coating. Variable slider allowing you go to from ND2-400 easily to make your photo the desired outcome you want. Nicely packaged aswell.

VND Filters are tricky, and mileage may vary based on a lot of factors.

In optics, no matter how many tests you run, each one of the elements before the camera sensor will play a role on the outcome, especially when dealing with mid range filters.

K&F makes a lot of good gear at a reasonable cost, fixed ND filters are more predictable as VND Filters limit the light that passed in a similar way a CPL does, but between two optical layers, so the way the light then reflects on your lenses, and each one of its elements, then on your sensor, is a little bit unpredictable.

There is no color cast on my tests with this VND filter, and performance is good between 0-80% of ND Power, which would roughly be consistent between 1 and 7.5 stops of light.

Now, going beyond that, the dreaded cross showed on my viewfinder, took a couple of shots and confirmed the issue, however it was VERY SLIGHT, but got really north of 90%.

Now, i switched the filter to a different lens, one with a step up ring (natively 77mm, stepped to 82mm) and there was no cross until say 95% ND power, this leads me to believe that as expected, at this price range, results may vary, i find it very usable up to 95% on both the lenses i tested, as the issue can be fixed even for my native 82mm in post as vignetting was uniform on all 4 corners up to 90%, beyond that, yes, it's pretty unusable.

There's good value, good construction, good presentation on this product, unfortunately lost a star due to not being able to cover the whole ND range that was advertised and not being able to be consistent across different lenses, still a good buy and a solid purchase at this price point.