Directly fits my 70-300 lens which finally saves me messing around with rings. This one will be dedicated to that lens. I can't detect any interference with colours or vignetting that needs any correction during post processing. I rarely use my photos straight of camera but I have checked the JPGs and still detect no issues. Doesn't surprise me, I use filters from this manufacturer regularly and I'm not disappointed with this one. Excellent in my opinion.

I ordered it from this company as I have used some of their other products and they have been reasonably good. I needed a variable ND filter and this one seemed to fit the bill. It works similar to a circular polarizer and has some of the same pros and cons. The ND effect is marked on the filter edge and is pretty much right on. It gradually goes from dark to light and vice versa. The only real negative at least for me was the size of the filter precludes my lens hood from fitting over it so I have to put the filter on first then the lens hood. I could detect no filter caused vignetting even at the 14mm wide end in use. It also suffers from the over dark blue sky effects similar to a polarizer at ultra wide angles. Comes with some extra cleaning cloths which is a nice touch.

Overall a pretty good ND filter. The negatives are pretty minor. I am looking forward to using it on a couple waterfalls in the near future.

An easy 4 stars.

Ordered the 37mm diameter filter. Comes in an opaque storage box plus you get 3 microfiber cleaning cloths. Nice tactile response in adjusting the fader. Beautifully made and perfect fit on my Panasonic camera lens.
5/5

This product was sent to me for review, as part of Amazon Vine. The below is my own real-world experience of using it.

In terms of quality, it appears to have been well-made; the construction is robust, with a sleek finish and properly-machined fitments on all sides - I was able to attach it to my Lumix S series lens, without any issues. As far as the glass itself is concerned, I could see no unwanted blemishes or scratches.

As I like to use my Lumix S9 for videography, I have found this particular filter really useful for maintaining more 'natural' colours in my work, whilst being able to use slower shutter speeds (when needed).

In summary, a good value item, and a useful addition to the kit bag.

Very good range of ND stop ranges. The color is still decent and the contrast is less pronounced. Lenses longer than 70mm (full frame) there's no cross-shapped shadow on the darker settings but a very noticeable dark cross on my 35mm. I do wish there was an adjustment mark on both sides of the lens so I could see where my range is set.

This filter is a good ND if you've not used one before and want to see if it's a useful part of your arsenal (hint - it will be), or perhaps if you already have one but want better build quality. I have always found K&F products to be of a good solid build and this is no exception, with a nice amount of resistance to the rotation and a decent hard protective case.

My intention for this filter has been lightning photography, but I've sadly yet to get a storm for testing. I haven't noticed any problematic colour casts, but I'm not so concerned with this as it could easily be rectified with minimal processing. I'm awaiting a colour checker so I can test for any shifts at different settings and will update this review with example photos if any problems come up.

You only have to look at the cost of 'professional' variable ND filters to know that the very best results come at a considerably higher price point, and with that in mind you could do a LOT worse than this filter for a budget-friendly option.

As others have noted there is no hard stop when you hit maximum, but I'm not so concerned about such a feature at this price point and I'm not sure I will ever have cause to use it near maximum anyway.

A side note on ND generally - People use neutral density either for longer shutter speeds (smoothing the flow of water etc) or for widening their aperture (shallower depth of field and more bokeh). I find it useful for another purpose specific to mirrorless cameras - sensor dust. The lack of a mirror makes it VERY easy for small specks of dust to get in whenever you change a lens or activate a telephoto zoom (which blows/sucks air directly onto the sensor). So on bright days where you are forced to narrow your aperture to 16 or 22, sensor dust become visible as blobs in the final image. ND allows you to widen your aperture, which renders dust invisible. This is especially relevant if you take images that feature clear open skies. You could clean them up in processing but if you are doing timelapses it can become very problematic to fix.

I ordered this for my iPhone 15 Pro Max as I do spend an inordinate amount of time these days favouring it over my regular cameras.

It threaded nicely into the phone adapter and changing stops was smooth and easy, image results are what I would expect from a filter produced by this company, no weird artifacts ,vignetting or the dreaded X.

This is an excellent, premium filter!

Among many K&F Concept variable ND filters, the NANO-K series is perhaps at very low end of the price range.  I do a LED light reflection test for all filters.  The K series variable ND filter is in blue color, which is not good.  The picture color shift is very obvious, and for me it is almost unusable.
Now, this is a true color variable ND filter, though it is still a NANO-K series filter.  The LED light test makes a green color, similar to some true color ND filters from other manufacturers.  And there is almost no color shift, so it is very usable.
For people prefer K&F filters, it is good enough, but if you like to try other true color variable ND filters for some less-known brands, and at the similar prices, you might find better ones.

I really like this filter. It feels like a good quality filter and the optics look great with long exposure photos. I like that it can replace multiple filters and saves me from lugging around a bunch of extra camera gear. The filter itself feels like a high quality piece of kit. I am pretty happy with it.

This is my third filter from K&F Concept and the last two I still use every single day (I'm a pro photographer/videographer) and love.

This one is a super powerful ND filter that goes from ND2 to ND400 which is an incredible range and can handle just about everything from day to day shots, daytime and super bright days to just leaving on the lens at night for evening shots and it copes with both admirably.

Comes in a very protective case, with a safety string if you want to use it, and a cleaning cloth - nice touch.

The quality of the build is as you would expect from K&F - first class and will last for years.

The images you get are very impressive and require little to no colour correction thanks to it's ability to not add too much yellow to your images like others do. This gives the shots a nice balanced colour straight out of camera.

Compared to others filters in the market of this quality I think this filter is a bit of a steal. They could easily charge a bit more for this one.

If you're in the market for an affordable, good quality ND filter then choose this one and you'll be really happy I think.