I searched for some time a wide-angle fixed focal length replacement for my Canon 24-105 4.0 zoom. In question was the 24mm 2.8 IS USM and the 28mm 2.8 IS USM. After much deliberation I decided on the 28 as according to tests and Product Reviews offers a slightly better sharpness, (especially in the peripheral regions). I have now tested it on the 5D Mark II and am very satisfied. Border areas are marginally worse than the center and Aperture 2.8 also provides very satisfactory results. Chromatic aberrations are present in extreme contrasts, (as with almost any lens?). You can, however, software technology eliminate well. The 5th star it was not because I'm 50mm 1.8 acuity spoiled by "wonderful" Canon. In summary, a wide angle that the problematic combination full-format and wide-angle dissolves very well.
