As with other K&F filters, these are of spectacular value. The machining is excellent, and I like the design with large knurls to help screw them onto the lens.The optical quality is excellent. I often use this combination when shooting outdoor events like concerts, exhibitions, and parties. Adding these filters gives the shots a "finished" look that stands out compared to mobile phone shots of the same subject. The 1/4 black diffusion is very subtle; in most cases, it barely registers. It adds a cinematic look to the tone. The black diffusion really comes alive when there are specular highlights like backlit hair; then, the diffusion causes a subtle glow.The CPL filter does a good job of darkening the sky, reducing reflection and glare. It needs to be rotated to find the effect (The filter is designed to rotate without unscrewing). It's important to test the filter in the environment; in rare cases, it will cause unwanted effects like vignetting or the sky looking unnaturally dark but lighter at the horizon. It all depends on the lens and sun position.. But overall, this combination is killer for day exteriors featuring people.