Additionally, when the kit is setup for VNDs, removing a magnetized VND won’t immediately return your camera to “normal” exposure. There will still be the 1-stop VND base filter inside the base ring. You could of course remove the base filter, but for speed and convenience, it’s easier to leave it in and open the camera aperture or raise ISO a stop to accommodate. Looking at the 2-5 stop filter, I can get a range of 2 stops (a little before the 2 stop position on the ring) all the way up to 5 and 1/3 stops (at “5” on the ring), so the filter covers a range greater than the claimed 3 stops. I can see the benefits of convenience for such an attachment mechanism over screw in filters. I assume that they have been tested on lenses attached to bodies employing magnet IBIS technologies (as opposed to springs) and that on such bodies there is no magnetic field interference. I initially didn’t think much of having a clear UV filter to attach these magnetic filters onto. After nearly 15 hours on the move between climbing and hiking, I found a huge advantage to this additional filter. In addition to using the system as a CPL or VND filter, you can also replace the inner VND base filter with a “Mist” VND filter, which works just the same as the other VND filters but adds a “Glow Mist” effect, essentially a bit of diffusion that will smooth out your image a bit. I generally don’t like diffusion filters, so I didn’t test this heavily. The Only Problem

Like other manufacturers, Freewell claims that their variable ND filters are very color-accurate. However, VND filters are always critical to color shifts and therefore we should take the marketing announcements with a grain of salt. To truly know, we would have to test how accurate the VND filters are in the real world. Magnetic Filter System K2 – Source: Freewell FutureproofOne other advantage of the K&F Concept filters is that they are available for a wide range of diameters, starting at 49mm, as opposed to 67mm for some competitors. Freewell claims their magnetic VND system can be safely used with any 16 or 17mm full frame lens without adding vignette (on top of the natural, optical vignette of the lens). This means cleaner images without additional darkening around the edges and corners — even when shooting wide angle. Filter compatibility Remove the base ring filter, and there’s now one pane of polarized glass (which is effectively a circular polarizer is). The company also says the kit’s magnetic adhesion will keep the filters in the holder firmly affixed, which prevents vibrations while they still remain easy to remove and adjust. The metal knurling on the bezel along each ND level helps grip when turning to change values and allegedly improves the accuracy of stop setting. The company also claims that transitioning from one-stop value to another is smooth and gradual, and should give a reduced occurrence of “x-pattern overlaps” seen in other variable NDs. The downside to this filter is the colour cast. I personally am not a big fan of the green cast so I’ll have to correct that in post, each time I use this filter. If you do not like to post process your images, this may be a bigger issue to you.

In the tests I put each of these filters through I did not notice any significant differences in quality and sharpness. Rather than wasting your time talking about those two aspects, let’s focus on the areas that stood out; colour cast and ergonomics. Contrary to regular polarizers, the CPL has no moving parts. It rotates simply by moving on the adapter. This does generate a small friction noise. And then there’s the magnetized lens cap. It works fine with the base ring, but not with mounted filters. The lens cap removes filters when detached, which means you then have to separate the cap from the VND, then re-attach the VND. In fairness, I don’t think Freewell could have designed this any differently due to the magnetized nature of everything. One will just have to get in the habit of detaching a VND before using the lens cap. Feel free to ask me specific questions I might not have covered throughout this review or simply let me know what you thought. As always thanks for watching, reading, or both. Freewell says that its new system will be more convenient than others on the market, as shooters would only need to carry the two filters with them when traveling, and would still have the capability to capture images using ND stops from two to nine as well as having access to an integrated Circular Polarizer (CPL) and the “Glow Mist” bonus filter for creative applications.Each of these filters do exactly as they are intended to do. They darken the image by 10 stops allowing for longer exposures in brighter conditions. Each filter has it’s own unique colour cast, like nearly all ND filters on the market. The filter is basically a stationary magnet - like a bunch of bar magnets sitting on a table. I don't expect there is much impact on the magnetic actuators (which are magnetic motors) used in IBIS to move the sensor. Some of Fuji's best lenses use linear magnetic motors in AF - for example the Fuji X 50-140 f2.8 and the 90 f2. There is no evidence of any interference with IBIS and those two lenses so I doubt if small would cause any issues. I was expecting similar performance here with the Freewell filters, but I’m happy to report that they actually do a significantly better, as long as you don’t pay attention to the numbers on the edge of the filters too much. J. Matthew Gore Beach #3 on the Washington Coast, Freewell 2-5 Stop VND

Thus far in my experience, I have not had any issues with the filters falling off in standard use. That can be walking on a trail with my camera above my shoulder, moving with my camera in hand filming a shot, or even running around a bit. The filters are quite secure because they are machined well to fit within the ring that's attached to the lens. Thus not only are the magnets holding the filter in but the friction caused by the precision of the manufacturer helps keep them secure. They are also light so it would require a large impact for them to detach. I haven't been able to get them to come off in the field or in testing. Alongside the distinct Island Slot for gradient filters like a graduated neutral density (ND) filter, snow mist, glow mist, and streak, the K2 filter system also includes circular variable neutral density (VND), circular polarizing (CPL), solid ND, and graduated neutral density (GND) filters. Concerning sharpness and clarity, there is no discernible difference with the Freewell VND filters attached. Images appear just as sharp as you’d expect. Circular polarizers There’s always a possibility that adding a couple pieces of flat glass in front of your expensive optics will degrade your resolution, but I didn’t find that to be the case with these filters. Having tested on my 42 megapixel A7RIII and some of my sharpest lenses, there was no visible loss in resolution in the center or edges of the frame when using the Freewell filters compared to test shots with no filters. Cross Polarization ProblemsIn colder temps and time restricting locations, being able to just pull off a filter and slap another one on saves a ton of time. It would save your numb hands from trying to thread on and off filters, like you’ve had to do in the past. One other thing I wish they'd add is the filter details listed on the front of the filter. The details of the filter are listed on the side which is great but it would be nice to also include them near the thread size is. For example, if I have each filter in the case they come in, I can't tell which filter is which from a top-down view as you can see in the photo above. Not a deal-breaker but certainly something that could be easily changed. Magnetic System These filters feel good to use. Yes, you need to be careful as with any type of photography filter, but you don’t have to worry as much as when you’d use all glass square / rectangular ones. They’re light but don’t feel hollow. Their magnetic capabilities make them really easy to swap around when you’re out in the field. No more unscrewing and fumbling with filter threads on location. Just set your base ring to your lens, and from then on, it’s just magnets doing their magic. Colour cast is the hue that the filter gives your image. Kind of like how your sunglasses change the tint of everything you see, filters do the same for our cameras. Colour cast isn’t always a bad thing, however; some colour casts are more pleasing than others. Working with these magnetic filters was really a nice change from fiddling with fine filter threads, and I didn’t encounter any major problems with them. Of course, you do need to be careful when you’re detaching a filter so that you don’t fling it anywhere when you overcome the magnet’s grip on it.