K&F Concept 52mm Variable ND Camera Lens Filter ND2-ND400 (1-9 Stops) + Filter Cap + Cleaning Cloth 18 Multi-Layer Coatings Adjustable Neutral Den...

I bought the K&F Concept 72mm Variable ND Camera Lens Filter ND2-ND400 (1-9 Stops) for my Tamron 17-50 VC Canon mount lens, and Im using it with my Canon 77D. This filter works really well with my setup, allowing me to get the motion blur I need even when shooting wide open at a 2.8 aperture. The filters adjustable range is super handy for different lighting conditions. The price is great too, a bit lower than some of the bigger name brands, which makes it a good deal. It also comes with a filter cap and a cleaning cloth, which are nice extras. The filter feels solid and the multi-layer coatings seem to do their job well. Im happy with my purchase and will update this review if I run into any issues. So far, its been a useful addition to my camera gear.

Ive been a fan of K&F Filters for some time now, and have come to appreciate the consistency and the quality of the brand. The majority of my lenses live their lives with K&F UV protective filters on their front element. Like many others, as the caliber of mobile phone imagery and videography have improved to levels of near professional quality, Ive begun to concentrate more energy into taking advantage of those attributes, not to mention the portability. In hand, the K&F Concepts Variable ND 2-400 filter does give the impression of quality. In fact, I own the same K&F variable ND filter in a larger size, 67mm. All modern quality optical glass is coated to reduce reflections with K&F following that convention; the 18 multi-layers of anti-reflection coating the seller asserts are appealing and evident to behold. A variable ND filter works in a similar manner to a CPL, that is, there are two-rings, one that attaches it to a lens and the other that is turned to control the degree of transmission from more or less light, effectively allowing control of exposure. With that in mind, the K&F filter has a comfortable amount of thickness along with knurled edges on one of the rings that allows for sure-footed, precise control while being rotated. K&F has not skimped on material or fabrication. A ND filter, whether variable or not, is used to reduce the amount of light reaching a light sensitive material. In videography, it is generally used to follow the convention of a low ISO and a low shutter speed. In still photography, to allow for the use of a wider aperture in bright light situations. In either case, the benefit of the K&F Concepts variable ND filter is that the transitions between minimum and maximum light reduction are not stepped, but infinitely variable between its 1 - 9 stop range. In other words, one can set their camera to the desired settings, then rotate the light reducing transition ring to achieve the desired exposure. In my case, I ordered this Variable ND 2 400 filter in the 49mm size specifically for a 28mm f1.4 manual lens I own and that I want to be able to shoot at f1.4 in any situation; a variable ND with a 9-stop range allows me to do that. I can set the camera on manual everything, shutter speed, ISO and aperture at f1.4, then just turn the variable ND until the light meter or histogram tells me I have the correct exposure. There are two conventions for stating the amount of ND a filter provides, Optical Density Number, stated in thirds, with each third being a stop of density, for example .3, .6., .9, etc would be 1, 2 and 3 stops. The other is Filter Factor, the convention used by K&F. The Filter Factor rating is based on the actual amount of light reduction between stops, and is related to the inverse square law of light transmittance. Simply put, for each doubling of the FF number, there is a reduction of one stop of light. So, in the case of the K&F Concept ND 2 400 you have 0 2 = 1 stop, 2 4 = 2 stops, 4 8 = 3 stops, 8 16 = 4 stops and 16 32 = 5 stops; and so on. The K&F Concept Variable ND 2 - 400 Filter comes from a trusted manufacturer, is high quality in both fabrication and materials, and serves very well the need for which it's designed. That is, by facilitating the means by which the standard video convention of keeping shutter speed and ISO low, can be followed if so desired. It does this by precisely reducing the amount of light in brightly lit scenarios. In other words, it allows some control over otherwise uncontrollable circumstances. The filter is supplied with a case, a lens cap with lanyard and a cleaning cloth. The lens cap is a nice touch because as is very often the case with VND filters, the front threads are larger than the lens threads.

The K&F Concept 55mm Variable ND Lens Filter ND2-ND400 is a quick and inexpensive way to explore neutral density filters. As I had suspected, it appears that this works by pairing two circle polarizing lens and rotating one of them to darken the view. The stops aren't numbered, nor do they lock into place when turned. There are several dots to show you where you're at on the scale of min to max. When rotating the lens on the camera, it does so slowly and decisively. It's well machined and unlikely to move from where you adjust the stop. I found that when I set my DSLR to automatic (program) that it did slow down the shutter and open up the lens to compensate for less light coming in. The filter can screw firmly on the front of the camera lens or another filter. However, it has no threads to put a filter in front of it. It comes with a very good spring-loaded cover cap that a supplied lanyard can be used and attached to it. I doubt that I will ever want to use that. Not sure why they chose to put it in a plastic storage case which does protect it rather than a smaller, round type of case or even a vinyl envelope. Either would have worked and taken up far less room in a camera bag. I did not detect any color changes in the test photos I made. The only differences I could tell were the focus was slightly off. I'm not sure if that's simply user err or the lens interfering with the auto focus.