I mostly photograph weddings and I purchased the 14/2.8II because I already have the 24/1.4II and 35/1.4 and I was going to use these three lenses to cover the range that I normally cover with the 16-35/2.8II and the 15/2.8 fisheye lenses. I like the quality of primes because they minimally distort, are razor sharp, and are fast. At least, that's been my experience, and I was hoping to repeat it with this lens. What I found is that the 14/2.8II at f/2.8 is acceptably sharp at the center, but moving away from the center toward the edges it is very unsharp. The edges didn't sharpen much until f/5.6, with full sharpening by f/11. This is worse than the 16-35/2.8II, which is generally sharp throughout the entire image starting at f/2.8. Also, the 14/2.8II still retains the 6 bladed aperture to produce a 6 point sunburst flare, which does not look realistic, while the 16-35/2.8II has a 7 bladed aperture that produces a 14 point sunburst. So, shooting into the sun or at night with streetlamps, all of these point sources of light have sparse-looking 6 pointed stars. After shooting several images side-by-side with the 16-35/2.8II, I realized that I can step back with the 16-35/2.8II to get the same focal length as the 14mm, then correct barrel distortion in LR4 to get an image that looks virtually identical to the 14/2.8II, yet of better sharpness. Also, unlike the 16-35/2.8II, this lens has a purple fringe up to f/11, and it is noticeable on backlit subjects. The AF on this lens (using center AF point) focuses slightly better than the 16-35/2.8II in low light by about 1/2 stop. But, using using AF points farthest from the center (on the 1DX) produced out-of-focus images, no matter the light. Focus and recompose was the only way to get off-center compositions to be sharp. I'm not sure if the glass being convex is the cause of the AF not being accurate away from the center, but this is not a problem with the 15/2.8 fisheye, which is also convex. The 16-35/2.8II and my other lenses don't have this problem either. Basically, I expect a prime to be better than a zoom in nearly every respect, particularly at its widest aperture. This lens is only better in its elimination of barrel distortion and nearly everything else is worse than the 16-35/2.8II. Well, OK - it does have less vignetting than the 16-35/2.8II wide open. But, this is basically a f/5.6 lens with edge-to-edge sharpness becoming equivalent to the 16-35/2.8II at f/11. I do not consider this to be a lens for anything but landscapes and architecture, where most images are photographed at f/11 and higher.