bought this K&F Concept 14mm 2.8 to discover a genre of photography that I hadn't experienced until this moment, as the wide-angle focal I had was the 24mm of the Canon zoom that I use on my 6D. I had this goal for a long time because, to read on various forums, it is considered a very good product that, at a very attractive price (about 350€), gives performance really well. This K&F Concept lens is a bit special because, unlike most lenses, it's totally manual, it doesn't have a chance to be controlled by the camera (this is for the Canon model, the Nikon model has the electrical contacts that the Allow the camera to use the TV recording mode, view the focus through the viewfinder (when the green dot indicates manual focus) and record Exif data.With Canon, as mentioned above, the operation is completely manual, it can only be done in the M recording mode can be used, the aperture can only be varied via the mechanical jerky ring in 1/2 stop increments from F/2.8 to F/22 and there is no way to compare the Exif data with the aperture values on the file I decided to buy it anyway, because everyone praised its optical properties, which were awarded even at TA After the first tests, I can only confirm these opinions, the sharpness of this target is really exceptional even at F/2.8, it is pretty much a blade...! Unfortunately it's not all gold that shimmers...!! This K&F Concept has some flaws that can be important or nonsense depending on the use you intend to make it...!! One of the flaws I've found (like so many others who use it) is the distortion it creates, which is very specific..., I saw barrel, pillow distortions... but I was missing those. ..!! It's what many call a “mustache” distortion, it's non-linear, it forms a sort of wave that's not very easy to correct even in post-production with the various lens corrections of image processing software. If you use it for panoramic photos you won't notice this flaw, but if you take photos of architecture it can be annoying a lot. Another flaw is that since the aperture of the manual membrane, if you shoot with fairly closed membranes, with not excessive light, you will have a dark image in the viewfinder, since the lens does not have the ability to adjust the aperture at the desired opening only to Closing time of recording...! Then we talk about the focus..., the lens is only manual and that is known, but precisely for this reason it is unthinkable that the focus ring is completely staring..., for the infinity focus I have to refer to the value on the Adjust notch of 0.7 mt...!! A manual focus lens is used the vast majority of the time in IPERFOCAL, it's not easy to do this when the readings on the dial don't match the real ones...!! Of course..., in this case it's an ultra wide angle, it's certainly not impossible to do that, especially if you're using fairly closed diaphragms, but I don't understand how K&F Concept are selling these lenses with this apparent flaw can (it's a problem that afflicts almost all specimens on the market)...!! Another thing... if you use polarizing filters or other filters, keep in mind that this lens has the petal type lens hood, which is fixed and cannot be disassembled, you cannot use normal threaded filters, but you need a special filter holder buy for plate filters, which are quite expensive. Personally, although I was impressed by the quality of the images that this K&F Concept can emigrate, I decided to make the return since the errors present do not allow me to find ourselves feeling good, I'm really sorry but I believe that a good lens is not only made by good optical quality, but must be able to be one with the photographer and with that, at least with me, it didn't happen...!