The Better Alternative to Variable ND Filters: Fstoppers Reviews the Freewell Magnetic Filter System

I wanted something to control my exposure when shooting videos but I didn't want to sacrifice quality with a variable ND filter. To my surprise, the magnetic system by Freewell has been better than expected and even has features for photography that have replaced my older equipment. 

When I was searching around for solutions to controlling my exposure the most common answer was to use variable ND filters because they are the most convenient and practical. Their convenience comes at the cost of image quality and adding a potential failure point. I did a lot of research and decided that the image quality loss I could live with but wouldn't be happy about. What I didn't want to deal with was the potential of ruining shots because many variable ND filters can cause cross patterns of polarization by over adjusting or bumping them in the field. If you want to know more about what I'm referring to check out the best comparison review on variable ND filters out there by Gerald Undone. When I learned what issues I might face using a variable ND I started looking for alternatives but knew I might have to settle for a variable ND if I couldn't find something that was quick in the field.

I stumbled upon Freewell's magnetic ND filter system and realized it was exactly what I was looking for. I wanted the image quality and peace of mind from an ND filter but also one I could change or remove very quickly. My biggest concern was the system's reliability of staying attached in different circumstances such as walking with my camera in hand or possibly running to catch a shot. I test all of this and go over all of my thoughts within this review.

As a disclaimer, I had this system in my cart ready to check out before reaching out to Freewell and seeing if they would be interested in me writing a review for this system. They happily agreed and sent me the filters used throughout this review. They never asked for a positive review, to see the review before it is published, or anything of that nature. Thus everything within this review is my 100% honest opinion.

Build Quality and Features

Each filter comes with a threaded ring that screws into your camera lens just like any other filter you've used in the past. The difference is it's just a metal ring that does nothing until you attach a filter to the ring using it's magnetic system. Freewell also offers the option to use a UV filter as the magnetic ring for it's system but I didn't use one in this review. 

Personally I use a UV filter on all my lenses for added protection from the elements or the extra safety it may provide in a fall thus it's a fantastic option, but not something that would have worked for my video camera. I have to use a step up ring to go from my Fujifilm's 58mm thread to the 77mm filter size I'm reviewing. The smallest filter size Freewell makes is 67mm meaning I needed to use a step up ring regardless thus I opted into using 77mm filters so I could interchange them from my video camera to my photography camera which has actually been fantastic — more on that later.

Overall the build quality is what you'd expect from a filter of this price, which is roughly $100 per filter. The threaded rings that screw into your lens are made of all aluminum and have a distinctive gnarl to them to help when screwing or unscrewing them but the beauty of this system is that you shouldn't need to do this very often if ever. Ideally, you just leave the filter ring(s) screwed into each of your lenses and add whatever filters to them on the fly. These rings even have threads on the inside so if you wanted to use a non-magnetic filter with them still attached, you can. 

The filters themselves also feature an all-aluminum frame with Schott B270 multi-coated glass making up the ND filter. I'll admit I don't have the authority to tell you if the glass and coating process on these filters is the best or the worst based on just what's listed on the spec sheet. Honestly, I don't care what it uses as long as the image quality is great (more on that below) and if the build quality feels solid which it absolutely does. On top of all of this Freewell offers a lifetime warranty on its filters as long as you purchase them from a reputable dealer which implies to me confidence in their quality. 

Lastly, each filter comes with a magnetic lens cap that works with the filter and the filter ring. The lens cap is also made from aluminum and is quite sturdy however it comes at the cost of weight. This weight isn't substantial but it will put the magnets in the system to the test which I go over further down in this review. I did test to see if your standard lens caps will fit into the empty magnetic ring or an attached filters and the ones I tested do fit but they don't go on entirely and don't sit flush within the rings. This is because the filters and rings are so thin there just isn't enough room for a standard lens cap to fully attach. You can certainly get by using your lenses stock cap with this system but it may not be as secure as you'd like. Regardless the magnetic caps that come with this work but I'll admit they are the weakest part of this design and I think there is room for improvement.

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

The main feature of this system is the ability to add, remove, or change filters very quickly. Let's say you have a 3 stop ND attached to your lens but needed to exchange it for a 6 stop ND, it would take only a few seconds to remove the current filter and attach the new one. Compare that to a traditional system of unscrewing the 3 stop ND and having to screw in the 6 stop ND which takes a lot more time. Not to mention if you need to swap it again later because the light is changing it can eat up even more time. This doesn't sound like a big difference on paper but if you've ever been trying to setup a shot where the light is fleeting you'll know exactly how valuable each second is.

Another convenience is being able to swap a filter from one lens to another. Many times I'll find myself swapping lenses for a shot but still needing my circular polarizer that was on the lens I just removed. This isn't an issue with the magnetic system whereas previously it meant I might not shoot with a polarizer when I should because I didn't have time. Have you ever been out in the field when a filter has gotten stuck likely because of a temperature change from when you attached it? I certainly have and it's not fun. Something you don't have to worry about with a magnetic system. There are probably even more benefits to this system that I haven't encountered yet but these alone were enough for me to be sold on the system... but let's tackle what you are likely asking yourself: will they fall off?

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. 

The lens caps are a bit of a different story. Considering they are solid aluminum they have more weight to them and they also don't have as big of a groove that attaches within the filter or magnetic ring. The cap has come off in certain situations or when I've tried to force it to fall off in testing. Thankfully it's just the lens cap, which I'm sure all of us have dropped or misplaced at some points in our careers. However, it's still something that I think can be improved to be a bit more secure and something I'm mindful of.

Lastly, I discovered how easy it is to pack these filters away. I typically keep all my circular filters in their own case (I only have 2) but I know many people out there have a lot more than me. You can actually just stack these filters together and throw them in a pouch or case together with no issues. Above you can see the 3 filters stacked and ready for storage. 

Overall the benefits of this magnetic system greatly outweigh my concerns of reliability which in my testing hasn't been an issue. 

Image Quality

This isn't going to be an extensive scientific test or comparison for this section. I'll be using photos instead of video for these tests simply because photos give us more detailed results. I used a Canon 5D Mark IV with a Canon 70-200mm f/2.8 II lens set at 70mm for each shot. I shot two comparisons at f/2.8 and f/8 to compare the color cast and sharpness. I used the Freewell 1.8 ND (roughly 5 stops) to give a solid overall representation of what you might experience regardless of what ND level you purchase. Typically as you increase the strength of the ND there will be more color cast, ie a 6 stop ND filter will have more color cast than a 3 stop ND filter. 

The first comparison is shot at f/2.8 which gives us the strongest vignette representation. As you can see the filter adds a bit of green tint and coolness overall. No matter what filter you use this slight shift will happen, it's just the amount that it shifts that demonstrates how well a filter is made.

The second comparison is exactly the same just shooting at f/8. The color shift is essentially the same but notice the tiny bit of vignette being caused by the ND filter. This wasn't as obvious at f/2.8 but you can see it here. It should be noted that the wall I was shooting was not precisely lit and was certainly brighter in the top left than in the bottom right. I did this on purpose because it's a much better representation of real life rather than a precisely calibrated measurement.

This slight vignette at 70mm got me curious how bad it might be on my wide-angle lens so I moved to a different wall and tested the vignette on my Canon 16-35mm f/4 with it set at f/8 and 16mm. As you can see there is a very tiny amount of added vignette but it's completely negligible in my opinion which is fantastic at 5 stops.

Lastly, I zoomed into 200% on the images taken at f8 with my 70-200mm lens to show potential sharpness loss. Such detail likely won't come through after jpeg compression and resizing for this article but trust me when I say I see no loss in sharpness or detail in the image, which is great.

I'm more of a practical person when it comes to reviews and I don't necessarily need a bunch of lab tests, pixel peeping, or endless comparisons. For this, I just wanted to see how much color cast is added and if I lose any quality overall. As expected with any ND filter there is a bit of a color cast but nothing extreme that wouldn't be fixed with a few white balance adjustments. I think the image quality from these is excellent and on par with the more expensive filters I own.

Photography

I wanted to do a quick section on this because my main focus in this review was using this system for video work instead of a variable ND. That said a lot of the benefits and concerns I've listed throughout this review apply to photography. As a landscape photographer first I thought it might be good to include benefits I've found that I didn't expect for photography.

If I have the time I use a filter holder system by Wine Country Camera. One of the main purposes that many landscape photographers use this type of system is the ability to stack filters or simply change filters out quickly depending on the conditions. You can't do this quickly using standard screw-in filters, but you can by using this magnetic system. If I want to stack a 3 stop and 6 stop ND filter I could do so without taking much time, obviously disregarding issues with wide-angle lenses. The point I'm trying to make is by being able to exchange or swap filters quickly, this can be a good substitute for a filter holder system in some situations.

The filter I use the most in landscape photography is a circular polarizer but as I mentioned previously if I need to take it off one lens and attach it to another sometimes I simply don't have time. Being able to swap a polarizer this quickly really sets this system apart from many others and I cannot recommend it enough simply for its convenience. There are times when I'm trying to capture a shot handheld with no setup time and it could absolutely benefit from having a polarizer but I simply never attach it because I don't want to miss the shot. Not to mention trying to screw a filter onto a camera you are holding without dropping anything can be a challenge as well.

Conclusion

Pros:

• Quickly add, remove, or exchange any filter.
• Easily stackable
• Solid construction
• No image quality loss
• Can stack and store them all together
• Filter rings have threads to allow you to use non-magnetic filters
• Lifetime warranty

Cons:

• Filters have the potential to fall off but haven't yet in my experience
• Lens cap could be designed to be more secure
• Lens cap needs a small lip or groove to remove easier without removing the filter
• Include filter description for top-down view

Overall I'd highly recommend this system to both photographers and videographers. Each filter is around $100 but you can get slight discounts by ordering in their packs of 3. This system solves the quality and polarization issues that variable ND filters have always suffered from while also being extremely useful for photography. If you're looking for photography filters, especially a polarizer, this is absolutely a system I would recommend. If you're like me and do both then it's a no brainer. Even though I only wanted a solution for my video work, after using this system it ended up replacing the B+W circular polarizer that I've used for almost a decade.

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.

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