I got my new K&F Concept Clip On 67mm CPL Magnetic Phone Lens Filter Kit today and anxiously opened it to give it a try. My first impression is that this K&F Concept Clip On 67mm CPL Magnetic Phone Lens Filter Kit is a well built camera phone accessory.
It is made of metal, aluminum I think, and is solid. It comes in it's own zippered case with foam packing that speaks of quality too. The nice feature about this K&F Concept Clip On 67mm CPL Magnetic Phone Lens Filter Kit is the magnetic method to attach the filter. The filter itself magnetically snaps into place with a firm grip. There is no concern that the filter may ever just fall off.
The K&F Concept Clip On 67mm CPL Magnetic Phone Lens Filter Kit connects via a thumb screw that tightens onto the camera screen to hold the filter frame secure. This is a bit concerning to me as I would think that if you aren't careful you could over tighten the screw and end up breaking the phone screen.
When I attached the K&F Concept Clip On 67mm CPL Magnetic Phone Lens Filter Kit to my Galaxy S23 Ultra, which has 5 camera lenses, it looks like the filter slightly blocks the bottom camera (Telephoto 1). However, as I switched between the camera zooms and I didn't see/notice any actual blockage of the lens. I will keep an eye on this as I use theK&F Concept Clip On 67mm CPL Magnetic Phone Lens Filter Kit more to see if any thing is ever obstructed by the filter.
The filter lense itself also is well made. It has an aluminum outer ring and fits nicely into the frame and the lens is made of glass that is tinted for the CPL effect.
In all, I give the K&F Concept Clip On 67mm CPL Magnetic Phone Lens Filter Kit a thumbs up, but I do worry about over tightening and cracking my phone screen.

TL; DR- Use the CPL filter most of the time and it's awesome. Fits my GoPro 9 perfectly and the storage case is actually quite good.

K&F magnetic filters - CPL, UV, ND1000 - Excellent choice ! Packaging : 6,5 / 10 Nice case that keeps the filters together and protected. With velcro and ring to attach it to a belt or backpack. I don't particularly like the plastic box, I would have preferred something ecological like for other brands, but it's not something important in use so it weighs less on the judgment of the packaging. Handling: 9,5/10 Excellent workmanship, the filter is metal, threaded which fits well into every lens in my possession. Great that they are magnetic. In some conditions, screwing on a filter is very difficult and time consuming as well as the risk of it slipping out of your hands. In the case of the K&F magnetic filters, you just have to leave the holder mounted. If necessary, simply move the filter closer to the lens and it will attach itself powerfully and precisely. This feature is the main reason to buy these filters. Optical quality: 8/10 ND filter: Excellent sharpness: there is no loss of quality in high contrast areas. As with most ND filters, the filter has a purple/magenta cast, nothing that can't be corrected in post-production (see photos - doesn't work on PC just to show the quality of the filters). Slight vignetting, but really slight, nothing major. Score : 8/10 Polarizer / CPL Filter: Very very sharp filter, no loss of quality when editing. It tends to slightly "warm up" the images, but again nothing that can't be corrected with a touch in post-production. Excellent reduction of reflections on water and leaves affected by bright light. I don't like the effect of the sky being too intensified towards the Blue color (which also happens with all the other CPL filters I've tested). Important note in this case, it does not produce any additional flare compared to a use without filters UV filter: I never use UV filters because I find them useless except in case of danger for the lens (salt / water splashes / resins, sand). I must say however that this one has a good performance, it does not lose sharpness or worsen the flare compared to the lens without filter. Quality/Price: 9/10 For the general quality of the filters in question the price is LOW. Such a kit is suitable for both demanding amateurs and professionals because the weak points of these filters are few and in any case surmountable, while the strong points (speed of use and sharpness) are more important.

K&F magnetic filters - CPL, UV, ND1000 - Excellent choice !
Packaging : 6,5 / 10
Nice case that keeps the filters together and protected. With velcro and ring to attach it to a belt or backpack.
I don't particularly like the plastic box, I would have preferred something ecological like for other brands, but it's not something important in use so it weighs less on the judgment of the packaging.

Handling: 9,5/10
Excellent workmanship, the filter is metal, threaded which fits well into every lens in my possession.
Great that they are magnetic. In some conditions, screwing on a filter is very difficult and time consuming as well as the risk of it slipping out of your hands. In the case of the K&F magnetic filters, you just have to leave the holder mounted. If necessary, simply move the filter closer to the lens and it will attach itself powerfully and precisely.
This feature is the main reason to buy these filters.

Optical quality: 8/10
ND filter: Excellent sharpness: there is no loss of quality in high contrast areas. As with most ND filters, the filter has a purple/magenta cast, nothing that can't be corrected in post-production (see photos - doesn't work on PC just to show the quality of the filters). Slight vignetting, but really slight, nothing major. Score : 8/10

Polarizer / CPL Filter: Very very sharp filter, no loss of quality when editing. It tends to slightly "warm up" the images, but again nothing that can't be corrected with a touch in post-production. Excellent reduction of reflections on water and leaves affected by bright light. I don't like the effect of the sky being too intensified towards the Blue color (which also happens with all the other CPL filters I've tested). Important note in this case, it does not produce any additional flare compared to a use without filters

UV filter: I never use UV filters because I find them useless except in case of danger for the lens (salt / water splashes / resins, sand). I must say however that this one has a good performance, it does not lose sharpness or worsen the flare compared to the lens without filter.

Quality/Price: 9/10
For the general quality of the filters in question the price is LOW.
Such a kit is suitable for both demanding amateurs and professionals because the weak points of these filters are few and in any case surmountable, while the strong points (speed of use and sharpness) are more important.

First off, I'm a fan of K&F's products, I try to use them as much as I can during photo sessions, since they just give good consistent results.

However, the ONE complaint I've always had, is that K&F's product line was quite limited to low to mid range products. Don't get me wrong, they are amazing for what they are.. and I LOVE having them on location. But, as with any product I use in the field, they're often NOT the same products I will used in a fully controlled environment. In a perfect world, I would be able to take all of my studio gear on location, and not have to worry about potential damage to my gear.

To that end, K&F's mid-range type of filters and equipment have worked extremely well..

However.. I've always wondered.. what if my preferred manufacturers actually produced higher end gear.. would the results be as good? Better? What might I be missing, by taking certain types of gear, over others?

When I saw that K&F was producing a 'Nano' sort of lineup, a while ago, I was excited.. but also somewhat concerned... I already had my high end filters that I would use on special occasions, and for studio work... would K&F be able to actually meet that quality? If so.. could I stop buying gear from manufacturers that I didn't want to use, due to their awful customer support practices?

When I saw this filter pop up on my recommended feed.. my curiosity got the better of me, and I had to order it.

I grabbed the 82mm version, since my primary workhorse lenses are 82mm. Sigma 24-70mm f/2.8 DG DN Art, is commonly my 'Go To', though having rented and used a Tamron 35-150mm f/2-2.8 Di III, a few times, now.. and having it on my wish list.. both use 82mm filters.

After using it for a couple of sessions, now... both studio and on location, I have some initial short term thoughts:

Exposure change is minimal. - This is a big deal, since so many 'cost effective' polarizers will often drastically impact exposure. I've seen some filter change the EV by as much as a full stop. At that point, a CPL is operating more like a slight ND filter, and is not really optimal if all you're wanting is glare reduction. This one, I would say reduced the EV by roughly 1/8th of a stop when installed.

Color shift also seems to be minimal, if there is any at all - CPLs are also often plagued with the problem of changing the color of a scene, when they're applied, and in the case of variable polarizers, you may even experience a color shift while adjusting the amount of filtering being applied. This isn't ideal, as it just means you're going to have to do more color adjustment in post. Now, that said, keep in mind, the way a variable CPL works, if that if you reduce the glare from a source that is producing a color cast, you WILL have some color shift. This is just the nature of light.. similar to using a gold colored reflector for a subject illumination. If you remove the gold color from the reflector, there WILL be a color change. This is not the same as a filter created color shift.

Distortion seems to be non-existent - This is ANOTHER problem that so many filters (in general) have, and can often be so slight, as to not be seen until you're working with your files (RAW or otherwise) in post. I've seen a large number of filters absolutely ruin photos in the past, so it's something I tend to be VERY twitchy about. This filter seems to have no distortion at all. I'm EXTREMELY happy for that.

Quality & build - This filter has 2 parts to it. When I say that, I don't mean there's 2 physical parts that you have to attach... just that there is the static mount, that attaches to the end of the lens, and the adjustable portion that floats and rotates on the end. The static mount is actually a bit on the small side, which means if you are going to be attaching this to your lens, with any bit of snugness, you may want to use a filter tool for it.

NOTE: This filter does NOT have a forward facing threaded mount. If you use a lens hood that attached via the filter threads, it WILL NOT WORK with this filter. Additionally, the lack of a forward thread also means you cannot stack this filter with others, OR you will want to use it as your last filter in the stack. I know.. there is some photographer out there, right now, reading this, who is screaming that you shouldn't stack filters, ever.. but you saying that, doesn't change the fact that there ARE those that do. If you DO still want to use the CPL as a middle filter, you're going to need to get some external mount adapters to do so.

Case - The case the filter comes in, is actually a nice little leather and denim case, with a pull string on the side, that will push the filter out for you. My only gripe with this case, as with so many others, is that it'd be nice if the case had a small insert for a label. When carrying around a kit of filters, and you're operating in lower light conditions, it's often a pain to read the edges of the filters to determine which one you're grabbing. Adding a small label pouch would be an awesome addition.

Un-important - The packaging of the filter is quite nice, having a sturdy foam framed box, and including a microfiber cloth is a nice touch. The fact that the box turns into a 'picture frame' is gimmicky, and borderline insulting, as if the average person buying this were a child, who may become super excited over using a dense foam-board package as a photo frame. It's a $180 lens filter... the person buying this isn't going to spend that, and then not buy a decent frame for any photos they produce. This sort of marketing gimmick might work for those individuals buying a $20 CPL for their instagram photos.. but this filter is clearly aimed at the higher end photographer.

So.. that brings us to the big question.. how are the results? Honestly, I can't find a reason to complain at all. Colors come through as expected, no distortion, and absolutely no image reduction. The smaller mount point on the front lens element keeps flaring down to a minimal, and produces nice, crisp fantastic images.

The variable polarization works as expected, but I would have liked to see it spread a bit more evenly around the lens. Right now, when I turn the adjustment ring, there seems to be an awful lot of lack of polarization for a good amount of the filter, before the polarization kicks in, quickly.. a more gradual approach would have been preferred, BUT, that's nothing different from the current high end CPL I'd been using, either.

Which brings me to the price... at the currently listed price of $180, this filter is squarely in the upper end pricing for a CPL, which is an area that is already a rough spot to be in, since CPLs usually start to lose their price to performance around the $100-150 range. The $180 range now places you clearly in the range of B+W, Zeiss, and Hoya... 3 of the big names that dominate that market spot. It DOES perform on par to may of those products, but then again, you also have companies like PolarPro that have been making leaps and bound in that area, too, with the latter being VERY aggressive in their price to performance. I've had experience with all of the above, and while I really like K&F's customer service, and the fact that they're a LITTLE cheaper than many of the aforementioned brands, it doesn't change the fact that they MIGHT be pricing themselves out of the competition. If this filter was aimed at a lower price point, say $130-150, it might be an easier pill to swallow, especially if you're the type that wants a separate filter for every lens in your kit (as opposed to using a step down/up filter set).

That said, so far I'm immensely happy with the results I'm seeing with this CPL, and I'm cautiously optimistic that my long term experience will keep me comfortable with this CPL... time will tell, but for now, I'm cautiously recommending it, even at its current price.

This is a really, really nice CPL filter. It has a very slim design so it doesn't result in any vignetting, even while using may long telephoto lens.

Threads onto my lens easily without issue.

Adjustment of the polarizer is smooth and predictable.

There's no color shift or any other artifacts from the filter. Just crisp images with accurate color.

The filter comes with a nice fabric storage case, along with a microfiber cleaning cloth.

There's also a little instruction card that details how to use the box the filter was packaged in as a photo frame. Kinda kitschy but whatever. I just tossed it.

Great quality though.

RECOMMENDED>

Use this filter a lot outdoors for cutting down on glare. This is a high quality filter and does not diminish the quality of my lens even slightly.

My circular filter kit for each lens size includes a protective UV, a CPL and ND 10 and 6 stop. The K&F kits contain all but the 6 stop. The 6 stop can be ordered separately, though at this time only from the manufacturer's website.

For any given size kit, the K&F Concept magnetic kit costs far far less than would top line individual threaded filters from other manufacturers (Breakthrough Photography, B+W, Hoya HD3, etc.). Yet the optical qualities of these K&F have been tested and are equal to the best. My own experience is that the K&F coatings are also just as effective at repelling water droplets as are my most expensive filters.

Having used K&F Concept magnetic filters in two sizes for a few months I am loving the speed of filter changes and the absence of thread jamming when I stack an ND on a CPL.

My only criticism is the lack of knurling on the front edge of the CPL frame. Magnetic CPL filters do not need or have a two piece construction. The entire filter is rotated in its magnetic attachment, which is fine but remains a two-finger grasping maneuver. To rotate the CPL you'll need to temporarily remove the lens hood. Maybe had K&F added knurling to the from edge a fingertip would suffice, but there is more friction opposing rotation than in a well made two piece threaded CPL. Off course you could attached your old threaded CPL to the lens, screw the open ring magnetic adapter onto the CPL, then add your NDs magnetically. You'd risk jamming the adapter ring to the front threads of your old CPL. I'm not going to do this.

The protective UV is only meant to be attached directly to the lens threads. It is a lens protector. It does not magnetically attach atop the other filters or the open adapter ring. You are give two threaded adapters, one is just an open magnetized frame. The other has the protective glass. The CPL or ND can be clicked onto this protective filter, but not the other way around. My advice is to use the protective UV when facing blowing sand or salt laden ocean mist (and when shooting from a Russian reindeer sleigh where showered by flying feces).

The included pouch is well made and easy to use. If you buy kits in multiple sizes you can even combine them into one pouch by storing the filters magnetically stacked and assigning each compartment of one pouch to a different diameter.