Tested the 14mm K&F Concept on a Nikon D750. The workmanship looks solid and also feels good. The positive: The size is very comfortable and the weight is more than acceptable. The image quality is absolutely convincing for this price. But I only tested aperture f8.0 and 9.5. Anything below f8.0 is absolutely not important to me. Since I only want to work hyperfocally at this focal length. Anything above f9.5 is outside the beneficial aperture for a 24MPix sensor, so nothing gets better when stopping down. My lens was surprisingly well adjusted in terms of sharpness. It was still well sharp in the corners and gave a good drawing. I tested it against my Tamron 15-30, 2.8. And the K&F Concept did relatively well. The autofocus is quite fast, but that doesn't really interest me with a UWW. The vision is impressive.....compared to my 15mm Tamron, the 14mm of the K&F Concept is amazing. The negative: This lens offers nothing more for good, old photo art. The AF is controlled by a motor, looks and feels great, but makes absolutely no sense to someone adjusting manually. Since there is no longer a distance scale here, I cannot use the lens hyperfocally. In very dark rooms, caves etc. you need a scale, otherwise it won't work..... In terms of sharpness, I can't recommend the lens for sensors beyond 25MPix. Compared to the Tamron 15-30mm, it already shows clear weaknesses in resolution....and that doesn't get any better with larger sensors, on the contrary. The big ones then rigorously point out the weaknesses. Conclusion: Great little lens, with enough sharpness right into the corners (if you can get a good one). Small and handy at a very reasonable price for this focal length. A top choice for landscape photography with sufficient light. For dark locations, you first have to turn on the light to see how the sharpness fades.