The Freewell K2 Versatile Magnetic Filter System combines the convenience of magnetic variable neutral density filters and standard magnetic neutral density filters with the ability to use a rectangular filter. As the number of rectangular filters is limited to just one, it’s not really a solution for dedicated landscape photographers, but it’s a good solution for content creators who want to switch between shooting stills and video on a regular basis.
Combines round magnetic filters with a rectangular filter
Enables quick changes in ND strength
Only one filter slot
Rectangular filters take some wiggling to fit
What is the Freewell Versatile Magnetic Filter System K2?
The Freewell K2 Versatile Magnetic Filter System reviewed here comprises a new holder and range of filters including magnetic and slot-mounted filters. The K2 holder is designed to mount onto lenses with a filter thread of up to 82mm and can accept Freewell Gear’s round magnetic K2 filters and a single rectangular (or shield-shaped) K2 filter can be slid into a slot. This means it can be used with a variable neutral density (VND) filter and a graduated neutral density (GND) filter or similar.
It’s important to not that the Freewell K2 Versatile Magnetic Filter System is not compatible with Freewell Gear’s existing magnetic filters.
Product type: Magnetic filter system with rectangular filter slot
Announced: 29th March 2023
Included filters: Starter kit: 1-5 stop variable neutral density (VND), 6-9 stop VND, VND base
Freewell K2 Versatile Magnetic Filter System price and availability
The Freewell K2 Starter kit normally retails for £406, but can be purchased for £285, while the Creative Capture kit, which will retail for £464, can be bought for £326, and the Landscape kit is £367 rather than £537.
Freewell Gear sells all the components of the K2 magnetic filter system separately, but there are also a few kits available. The Starter kit includes the Freewell K2 filter holder and the two compatible VND filters plus four adapter rings and a case, plus end caps to protect the filters when they’re not in use.
The K2 variable neutral density filters are made up of two components, the base VND filter which is held in a specific orientation in the holder, and two larger filters that are rotated in the holder to adjust the degree of filtration.
Although the VND filters are magnetic, they have hard stops so you can’t over-rotate them and introduce black crosses.
The ‘weaker’ of the two VND filters offers 1-5 stops of neutral filtration while the ‘stronger’ one is a 6-9-stop filter. These filters can also be flipped and used without the base VND filter to become a circular polariser (CPL) and a ND32 (5-stop)/CPL filter respectively.
Before a rectangular or shield-shaped filter can be used in the Freewell K2 holder, the covers over the slot need to be flipped back. Freewell Gear calls this part of the K2 system, the ‘K2 Island’. These covers ensure no light gets in behind the circular filters when they are in use, but they open to allow slot-mounted filters to be used.
The K2 holder cannot accept any of Freewell Gear’s existing filters including its original Magnetic VND Filters.
Build and handling
The Freewell K2 filter holder is a little slimmer than the average filter holder, but that’s partly because it only has one rectangular filter slot.
It’s main body, release buttons and locking screws are made from metal which gives it a durable feel.
As usual, the first step in using filter holder is to mount an adapter ring on the lens. The Starter kit includes four adapter rings to enable the holder to be mounted on lenses with 67mm, 72mm, 77mm or 82mm filter threads. Other adapter rings are available from Freewell Gear and the minimum size currently offered is 52mm.
With the adapter ring on the lens, you need to press the rectangular red buttons on either side of the holder so that it can be mounted. Releasing the buttons, keeps the holder on the lens, but the red locking pins should be rotated to keep it in position securely.
If you’re planning to use a variable neutral density filter, the next step is to mount the round VND Base filter. This has a small tab that slots into a reciprocating notch in the holder. When it’s in place, you should be able see a small graphic on the filter’s tab and read ‘VND BASE’.
No filter in place
Base ND in place
Now you can mount the VND filter of your choice to cut out 1-5 stops or 6-9 stops of light. You should be able to see ‘TRUE COLOR’ and ‘1-5 STOP’ and or ‘6-9 STOP’ – indicating that the filter is the correct way round.
The VND filters pop smartly onto the rim of the K2 filter holder, however, they need to be rotated to enable them to seat correctly so the hard stop feature works – you’ll feel it snap into place.
Once the VND is correctly mounted, and when the holder is orientated with the small spirit level (bounded by two white arrows) on the back is at the top of the lens, you should see a small white arrow on the red rim of the holder at the 3 O’clock position (as you hold the camera for use). This is the marker to set or read-off the degree of filtration. When the filter is correctly seated, it can only be rotated between the two extreme ends of the ND filtration.
The rectangular filter slot, the K2 Island, is revealed by pushing back the ridge plastic sections at the top and bottom of the holder. These pivot around sturdy-looking pins on either side of the holder, and they can be pushed back until they rest on the lens barrel.
Freewell Gear’s K2 slot-mounted filters such as the K2 0.9 soft graduated ND filter and reverse gradient filter are supplied mounted in a rectangular metal frame. Others such as the K2 Diffusion Snow Mist and K2 Cinemorphic Gold Streak are shield-shaped and have an appropriately shaped metal frame. Both types of frame have a wide tab at the top with ridges to give a good grip and are clearly labelled on both sides with the type of filter.
The filters fit snuggly in the slot in the holder and take a little wiggling to get them to slide down into position. The frame of the rectangular filters also tends to catch on the bottom of the holder as they are extracted and, again, a bit of wiggling is required. It means that you need to take care to support the lens as your fit or remove a filter.
My first impressions of the Freewell K2 VND and ND filters are that they are close to neutral. My images benefit from a minor tweak to the white balance to warm them slightly to match the results captured without a filter, but they are impressively similar straight from the camera. I found this to be true whether shooting using the Sony A7R IV’s auto white balance setting or a preset value.
My tests also indicate that the 6-9-stop rating of the ‘stronger’ VND is a little on the generous side, it’s closer to 8-stops, but it’s not uncommon to see that variation. Similarly, removing the Base ND filter and flipping the 6-9 VND to use it as a 5-stop ND filter extends the shutter speed by a little over 3 EV.
Optically, the filters are good with only a slight dip in the level of detail in the images captured using the 61MP Sony A7R IV when they are in place. This is only visible when you pixel-peep images at 100% on a computer screen. Zoom out so the image files a 27-inch screen and you’ll struggle to see the difference.
Some images also have a slight drop in micro contrast, but that’s easy enough to address when processing the images/video.
It’s handy to have a small spirit level built into the K2 filter holder and this helps to ensure that the transition of a gradient filter is level when you’re photographing a seascape or other scene with a level horizon.
The Freewell K2 Magnetic Filter System is an attractive proposition for content creators who want to shoot video and stills, anyone who wishes to swap between using a variable neutral density filter and standard neutral density filter have the option to combine them with graduated filters or creative filters.
Freewell’s K2 holder mounts easily and securely onto a lens, and using a separate base VND filter makes the larger VNDs more versatile so you don’t need to carry quite so many big filters.
The rectangular and shield-shaped feel well-protected by their frames, and there’s reduced risk of getting fingerprints on the glass. However, it takes a little jiggling to get them to slide fully home so it doesn’t feel especially slick.