This K&F Concept Slim Variable ND Neutral Density Filter comes in presentation type cardboard box (handy for gifting) with the actual filter inside protected by a plastic ‘clam-shell’ type storage /carry case. It’s also complimented by three cleaning cloths. I chose the 77mm filter thread size and is graded as being true colour ND2-400. The machining is first class with a very well precise thread that slides effortlessly on my Canon 17-40mm lens. The adjustable control is a joy to use as the turning action is nice and crisp and does the job of fading out unwanted light. The actual degrees are marked -etched on the rim of the filter in white and using ‘live view’ makes it easy to see the change as you twist the element and certainly helps eliminate blur in some of my photos.

18 coatings on the lens...well that's a lot of coating and this is just the lower budget K series range to K&F's X and X-pro series which have 24 coating layers. I am reviewing the 67mm Nano K-series here, but I also own the Nano X series of this same ND2-400 filter at 77mm which is about twice the price.

So whats the difference? Well having only so far tested this K series filter on a waterfall video scene on my monitor, the only difference is in packaging and presentation. Performance-wise, this filter seems to perform as good as the X series one.

As shown in my photos, The filter shows no flare, chromatic aberations, or cross effects. Once I have taken it out for more real world sunny scenes, I will know for sure and update my review.

So, in other worlds, this feel as high quality as the more expensive equivalent variable X-series filter.

However, when going to approximately 7 stops and over, the colours seemed washed out. Under 7 stops, the colours really pop. At all stops, the picture is sharp in the focus areas.

At this point, this feels like terrific value for quality results.

Just one grip, I have. There are no intermediate markins for the ND values or stops. Just notches. And there are no clicks, it's all continuous. I would have liked some click stops. But its a very minor grip at this price.

One more thing, as shown in my photo, this works and threads smoothy on my K&F step-down rings.

This comes well packaged and in its own sturdy plastic storage case, I am pairing it up with my Sigma 16mm lens.
The filter has plenty of scope for stepping the light down ND 2-400 and produces a nice image.
The rotation is smooth and accurate , I will mostly be using it on brighter days and for images were I require the light coming in stepped down but with plenty of scope.

As the K&F Concept 72mm True Color ND2-400 Slim Variable ND Neutral Density Filter is, in truth, still a budget filter, I have rated it 5 stars despite its obvious issue, common to many VND filters, of an X being visible when the maximum density is exceeded (not a literal X, but a cross shaped variation of light and dark) although, from my observation, this wasn't as pronounced as my low-cost budget version! (but this was under studio lights, not the bright, sunny, day I wanted)

The adjustment ring can be turned continuously, with no stops at minimum & maximum, so it is easy to exceed the maximum density and have the distorted cross shape (I believe the 2 elements of the filter are polarised, so the pattern appears at almost 90 degree difference) appears, and may not be noticed until the shot is taken. (don't ask...)

The photos above were taken:
No filter
Filter at minimum
Filter exceeding maximum - where uneven lighting of the frame is clearly visible.

If the weather improves later in the week, I'll add some outdoor shots.

Examining the RAW images in Lightroom, there are minor colour differences between no filter and filter, but so low as to be accepted as possibly just illumination difference.

This product comes inside of a cardboard box; once opened, you'll see 3x microfibre cloths and the ND2-
400 product itself. After reviewing this product, it is priced at E32.99 - I think it is of value; the product fits perfectly on my 67mm lenses and works very well.

The product does exactly what it is designed to: filter out light; due to ND 400, it can filter up to 0.25% of all light - the ring allows you to change this to however much you need; it helps me with long exposures or motion blur.

I would definitely recommend this product.

I have several neutral density (ND) filters to use with my mirrorless camera, but this K&F Concept 82mm True Color Variable ND Filter is the first with variable ND. Rather than changing filters or stacking filters to achieve the desired level of light reduction, it is only necessary to rotate the filter to vary the level of light. Variable ND filters come in a wide range of price points, and this filter seems to fall near the middle or upper middle of the range. I have several K&F Concept filters and have found them to be high quality, and this variable ND filter is no exception. In addition, this filter also is listed as a true-color filter, without the color shift that can occur with ND filters.

The 82mm threads on filter fit perfectly on my lens. The outer diameter of the filter was slightly larger than my 82mm UV filter, but the lens cap for my lens still fit on the filter. However, I was not able to put my lens hood on over the filter due to the slightly larger outer diameter. I also tried to put the lens hood on first, but it was pretty much impossible to align the filter with the threads on lens and tightening the filter to the lens would have been hard had I been able to get that far. A minor drawback of variable ND filters (or CPL filters) if you manage to install a lens hood, it is awkward and difficult to rotate the filter with the lens hood in place.

I shot a set of pictures at ISO 200 and f/8 aperture priority to check for any color shift. The filter has 13 tick marks between the “MIN” to “MAX” points labeled on the filter. I took a photo at the MIN point, followed by rotating the filter two tick marks and taking another photo, and then continued to follow the two-tick-mark, snap photo pattern. The level of light reduction by the filter is not linear with respect to a constant degree of rotation. The first three photographs all used 1/500 for the shutter speed, and it was not until the fourth photo (6 tick-marks in) that the shutter speed dropped to 1/400. As the tick-marks started to approach the MAX point, I changed the filter rotation amount to one tick-mark for each photo, as the light level was stopping down rapidly. The last two tick marks were taken with a shutter speed of 1/30 and 1/10, respectively, and the MAX point shutter speed at 1.6 seconds. I also took the same picture without the filter in place, to check for any color shift. As far as I could tell there was almost no color shift until the MAX point was reached. The photo taken at the MAX point – f/8 and 1.6 seconds shutter speed – had a very blue cast to it.

To check on the blue shift at MAX, I also tried a second set of pictures of maiden grass blown around in a light, intermittent wind. I again used aperture priority f/8 and ISO 200, and took photos at MIN (1/60 sec), 1-tick under MAX (1 sec), 1/2-tick under MAX (2.5 sec), and MAX (10 sec). The blue tint appears very slightly at 1-tick under MAX, is slightly more pronounced at 1/2-tick under MAX, and again was quite visible at MAX. So, color-shifting with the filter is pretty much unnoticeable until the filter is rotated almost to the MAX point.

Overall, I am quite happy with this variable ND filter. The color shift as the filter stops down is not noticeable until it is almost at the MAX point. When approaching the MAX point there is a blue shift, but the color-shift is correctable in Lightroom or other photo editing applications. The filter appears to cover a 9-stop range as advertised, with most of that range occurring in the upper 1/2 or 1/3 of the filter’s rotation range.

Very good ND filter, it does not detract from the focus, it does not affect the sharpness of my images or change the color. The variable filter works very well and allows me to maintain the aperture of my lens to maintain the depth of field to the degree I want. It is very well made with excellent quality crystals.

I’m relatively new to DSLR photography but I really am enjoying my new hobby. I have a Sony A7 iii and 4 lenses so far and this is my first filter, it most definitely won’t be the last. I mostly photograph my dog and landscape photos; we have a wonderful landscape of a nice pine forest and gentle hills my photos were often rather stark and just lacked a good definition and colour. I didn’t even know that you could get variable ND filters until I saw this one. Since this arrived the weather has been miserable and I really wanted to see how the filter worked so I took some indoor pics of a multicoloured lamp and I am impressed with how the filter performed, can’t wait till we get some good weather. I played about with different settings and the difference is amazing. I am looking forward to going to the loch in a week or so now. The filer fits perfectly with or without the lens hood and I can pop the lens cap over the filter. There are 3 cleaning wipes included.

Huge range of stops difference and works okay. There's not hard stops on the rotation so you can overshoot easily, and the marking for the stops is hard to read. On the Canon RF 28-70 2.8 I tested it on the marker to know stop location was in the most inconvenient spot possible. Like most other manufactures ND, you can't use your lens hood if you are using an ND.

While there is some color distortion it's surprisingly not that bad even at 9 stops. It was pretty impressive.

Overall it's a decent variable ND. Not perfect, but probably great for most people. I just wish it was a little bit more friendly to adjust and setup.

This filter is definitely great for specific jobs. For example, if you're wanting to shoot a shallow DOF outdoors whilst using flash, then the variable exposure that the filter can bring is incredibly useful. Straight out of the package, the filter itself is easy to screw onto my 20-60mm lens. The package also comes with two microfiber cleaning cloths for any smudges or dirt the filter may pick up on location.

The only negative I can say about this product is that unfortunately, If you want to put you're original lens cap back on, then you'll have to take the filter off. Once installed onto a 67mm base, the area the filter occupies becomes a little wider. This is annoying as I usually just keep my ND filters on the lens to save time.

However, in terms of performance, I see absolutely no fault with this product. It's incredibly easy to switch exposures by simply twisting the filter left and right. Definitely worth a try if you're interested in trying new tricks to controlling you're photo exposures!