/ 2.8 and 28 / 2.8 wide-angle fixes, the combination of very good optical properties, it is very good, comfortable indoors, although here (and only here) it can be inferior to the Canon EF 16-35mm f/2.8 I suggest looking at a few photos: 17 mm - page=0 17 mm, the sun is right in the frame - page=0 25 mm - page=0 not so sharp corners are cut at a wide angle, and color reproduction and contrast remain at their best, on the other hand, 40 mm focal length and f / 4 aperture at this focal length may not be enough, 27 mm EGF) without a pleasant near telephoto range (only up to 64 mm EGF, up to 80-85 mm is too far) I did not find it convenient on a crop camera.