[bdery]

Hi!

I had the change to test the magnetic filters from K&F Concept earlier this summer. These filters require a thin magnetic ring to be mounted "permanently" on a lens or lenses, and then when you want to mount a filter, it attaches instantly and magnetically. You can read more about them here:

Speeding Things Up: K&F Concept's Nano-Series Magnetic Filters - Light And Matter

There are a few companies making such filters. Freewell is possibly the best-known, their products look excellent, but maybe with a slight warm cast. Kenko's products are less widely distributed, but also good. The K&F Concepts filters are actually the best of the three optically, based on my tests (no effect on sharpness and no colour cast). They're also the least expensive. They even let you use your original lens caps, something Freewell doesn't allow.

At first, however, the lineup was more limited, with only a polarizer and ND1000.

Recently, they released an ND8 and ND64, but maybe the most exiting aspect is that they offer those two filters with a magnetic lens cap. I decided to try them (plus it gives me more mounting rings!)

Me being me, here's a short opinion piece about them.



The filters (both ND8 and ND64) come in clear plastic case.



Inside the case are three items: the filter itself, a mounting ring, and a lens cap.

The mounting ring is described in the article I linked above. Essentially, it's a very thin ring that you leave on your lens at all times. If you have several lenses with the same diameter, you can swap between them easily but you need a ring per lens (the PL+ND1000 kit comes with a ring and a UV filter which also acts as a mounting ring).

The new filters are exactly similar to the previous ones, and I'm happy to report that they're optically just as good.

The cool aspect of this kit (beyond the extra options of the new ND values) is the lens cap.



It's VERY thin, solid metal, frankly good-looking, and serves a dual purpose.



First, it can mount magnetically over filters or directly on the mounting ring (that's the best way to use it IMHO). But it's also threaded, so it can also screw on a lens (without the mounting ring). It then acts a bit like some of the DA Limited caps (for instance on the 40mm). I don't see myself using that, but it's there.



When mounted on a lens, it shows a very slim profile, and attaches quite firmly (almost too much so, until you get the knack of removing it).



The filters can easily stack, along with the cap, and because they're thin, it helps with vignetting or dark corners.

As you can tell, I REALLY like those. They seriously have no real drawback, and make it much easier to use various filters. With my wife and kids I can't spare the time ti fumble with filters, screw, unscrew, drop the PL when trying to mount the ND, etc. With the magnets, it's instant. Many of my lenses use 67mm, so I can use them on each. I have a Revoring fitted with a mounting ring, and use that on my smaller diameter lenses.

I've used filters from many brands, Irix, Hoya, B+W, Heliopant, Optex, Tiffen, and in particular regarding the polarizer this one from K&F is, seriously, the best I've used. No colour cast and no sharpness degradation. That company might not have the recognition of some other brands, but they appear to be just as good.

Here's the link to what I got.

https://bit.ly/2Zb5m3G

https://www.amazon.com/stores/page/592896B7-A7FC-4D38-841D-56EA963692C6?chan...netic%20filter

They also sell on Amazon, and they now appear to offer the CPL, ND8, ND64 and ND1000 alone (with the cap) in addition to the CPL+ND1000+UV kit.

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Last edited by bdery; 09-22-2021 at 05:11 AM.

[biz-engineer]

Magnetic filters, great. They may magnetize some lens parts and hijack the astrotracer compass even after the filter is removed.

[bdery]

Magnetic filters, great. They may magnetize some lens parts and hijack the astrotracer compass even after the filter is removed.

I haven't observed that with the lenses I use. It's possible in theory, but with lenses mainly made out of aluminum, that's not an issue.

I have never heard any report of this actually happening in real life. If that's a big worry for someone, then those filters are not the best choice. For the rest, they could be.

[jumbleview]

I assume this kit can be used with step-up ring, right?

[UncleVanya]

I have a set for the RX100IV.

[kypfer]

Magnetic filters, great. They may magnetize some lens parts and hijack the astrotracer compass even after the filter is removed.

Maybe not quite that extreme, but the magnet will probably affect the compass if using the GPS for geo-locating … could be a real nuisance if you're relying on the GPS info in the EXIF for subsequent work!

[biz-engineer]

Maybe not quite that extreme, but the magnet will probably affect the compass if using the GPS for geo-locating …

Compass and GPS are two different things. The compass measures earth magnetic field (via a small magneto-resistive sensor inside the same chip that also measured camera tilt, the one use for horizon correction..). GPS receives radio signal via an antenna from multiple geostationary satellite and calculate position on earth by some kind of triangulation method. The GPS won't be affected by magnetic ring on the lens, but the (very sensitive) compass will likely drift, indicating erroneous south/north directions.

[bdery]

I assume this kit can be used with step-up ring, right?

I would think so. Depends on your setup. If for instance you screw a step-up ring and a magnetic mounting ring on your lens, then it's just like a regular setup with a wider diameter.

If you want to screw a magnetic mounting ring, then assemble a magnetic step-up and then add a filter, it will depend on the weight of the end result. The magnets are strong but not THAT strong (they need to be removable).

What K&F Concept lack is a conversion ring to turn a regular filter into a magnetically compatible one. Kenko have that, and I've read that you can use Kenko magnetic filters with K&F components, but I haven't tested it.

[kypfer]

Compass and GPS are two different things. The compass measures earth magnetic field (via a small magneto-resistive sensor inside the same chip that also measured camera tilt, the one use for horizon correction..). GPS receives radio signal via an antenna from multiple geostationary satellite and calculate position on earth by some kind of triangulation method. The GPS won't be affected by magnetic ring on the lens, but the (very sensitive) compass will likely drift, indicating erroneous south/north directions.

Thanks for the correction … I was under the obviously misguided impression that as the compass feature in my cameras is only available when my O-GPS1 is attached that the compass was in the O-GPS1 … we live and learn

[jumbleview]

I would think so. Depends on your setup.

My set-up supposed to be next: in case I decide to buy the kit I intend to look for bigger size like 67 so lenses with 49, 52, 55 and 62 filter size can be used with corresponding step-up ring.

[bdery]

My set-up supposed to be next: in case I decide to buy the kit I intend to look for bigger size like 67 so lenses with 49, 52, 55 and 62 filter size can be used with corresponding step-up ring.

That's what I do. So you just need the proper step-up on your smaller lenses, and a magnetic mounting ring on those. Or you could use a Revoring, probably not more expensive on the long run. I also use 67mm filters, and on my smaller lenses that's what I use, with a mounting ring on it.

[mgvh]

@bdery: You convinced me to buy the K&F set, and the 72mm set I need went on sale on CyberMonday for $92. (It's now $115 on Amazon.) I'm eager to give them a try, because it was just too fiddly screwing the CPL on/off. Your review on lightandmatter was very helpful. Thanks!

[bdery]

@bdery: You convinced me to buy the K&F set, and the 72mm set I need went on sale on CyberMonday for $92. (It's now $115 on Amazon.) I'm eager to give them a try, because it was just too fiddly screwing the CPL on/off. Your review on lightandmatter was very helpful. Thanks!

I was glad to be of help! Let me know how you like the filters once you gain some experience with them.

[UncleVanya]

I was glad to be of help! Let me know how you like the filters once you gain some experience with them.

They’re on my wish list.

[mgvh]

So now that I'm getting started w/ the K&F magnetic system, any opinion on their Variable ND filters? And would you get the 2-32? or the 8-128? I suppose I'll see how the ND1000 that comes with the kit works first, since I have only used CPLs in the past. There is quite a price premium to get these magnetic ones compared to the screw-ins, but no point in buying screw-ins if they were too clumsy to use.