I ordered this polarizing filter for use on my Sigma 30 mm F1.4 DC DN Contemporary lens (my prime lens, not included); polarizing filters eliminate non-metallic reflections, thus enhancing scene detail and contrast. This is a superior quality polarizing filter whose polarizing action is easily verified by rotation while viewing an LCD monitor through the filter. The filter incorporates multiple coatings to prevent distracting optical reflections appearing within photographs. The filter machining is excellent: the threads attach cleanly; the filter rotates smoothly when lens-mounted. And the foam-lined filter plastic sturdy container effectively protects the filter while it sits in a camera bag.

It’s a nice pair of sunglasses for my Olympus

The filter is very well packaged and makes a high-quality impression. I've only been able to test it so far. It is easy to screw onto the lens and is easy to operate.

My fall to company for camera equipment.

I really love K&F concept's filters - they just work... every time. This CPL is both affordable and made with great quality glass. There's no vignetting on my 18-140mm lens. And most importantly there's no color shift like you get with other CPL filters. The threads match up with my camera's lens, and the adjustment ring provides just enough resistance to make adjustments smooth and convenient. This is an excellent polarizer, you won't regret this purchase.

I still shoot landscapes with a DSLR, and one of the 5 filters I use most often is a circular polarizer (CPL) because it helps to filter out the scattered light rays that cause glare on water, windows, and wet leaves, and that wash out the sky's normal blue tint.

There's not really a lot to say about a filter, though--does it do its job? Yes.
Does it do its job well? Yes.
Does it do its job well enough to be worth the purchase price? Absolutely yes--selling one or two prints taken with this filter will cover its purchase cost in profit.
Does it make it easy to take landscape shots that will sell? Skill plays a large part in that, but this filter does help to limit a few sources of the glare that can (not always) ruin landscape shots. It's also good in light tents and other situations where you have multiple strong light sources from different directions.

It's multi-coated glass, so they've paid pretty careful attention to limiting how much light this filter allows to bounce around, and to making it pretty much point-and-shoot once it's installed on your lens, even if you're still using the green box (full-auto mode) on your camera. This is my 4th CPL filter in different lens diameters; I've never had one be so great or so bad that I had strong feelings about it either way.

I have other K&F's and they have served well. Picked this up to go on my nifty 50, a "required" lens for the "serious". I use it on occasion, but not the best for birds and other wildlife. I expect it will help in the bright sun for flowers and such, but this time of year there is neither.

I was fortunate enough to have had the foresight to have a polarizer on my lens when photographing the geysers at Yellowstone NP. The difference was stunning. Since then I have always done my best to have a CPL for each lens, or at least one that could use a suitable adapter.

The quality is sufficient for an occasional use lens, and the price is right for such. Recommended.

I am comparing this to the Bower digital PL. It is 1/2 the thickness and is easier to use as the turning part has ridges spaced around it so you get a good grip and can control the amount of polarizing. I tested it today and it looks to be completely color neutral and no color fringing like I have seen in others. Price is right and I can highly recommend it.

Everyone who shoots outside needs a polarizing filter in their bag. The build quality and optics on this one seem excellent so far, and the overall feel is comparable to that of a more expensive filter. Rotation is smooth and natural, and the 77mm fit perfectly on my Canon RF lens.

This one is better on overcast days.
I have several of K&F’s polarizing filters. I find they have made me a better photographer.
Recently it snowed. I wanted to take photos of the pristine snow. The sun came out and the glare was reflecting off the snow. This filter toned down the glare and produced much better shots.
I now never set out for the day without this filter and my black K&F filter.