I shot a test series to examine Olympus M.Zuiko 17mm f/1.8 performance throughout the frame across a variety of apertures: f/1.8, 2, 2.8, 4, 5.6, and 8. If you prefer a more hands-on approach to evaluation, download the RAW files below and have at it: http://mu43rawfiles.s3.amazonaws.com/oly1718raw/PC230001.orf http://mu43rawfiles.s3.amazonaws.com/oly1718raw/PC230002.orf http://mu43rawfiles.s3.amazonaws.com/oly1718raw/PC230003.orf http://mu43rawfiles.s3.amazonaws.com/oly1718raw/PC230004.orf http://mu43rawfiles.s3.amazonaws.com/oly1718raw/PC230005.orf http://mu43rawfiles.s3.amazonaws.com/oly1718raw/PC230006.orf Meanwhile, if you don't care about ultimate edge and corner sharpness because you plan to shoot subjects where this doesn't matter so much, ie people, then see this series instead. And if you really don't care about tests and just want to share some of your photos with this lens, we've got a thread for that too. The zones examined in this test are shown by the yellow boxes below. 100% crops are then presented for each zone at each aperture. All processing was done from RAW in Lightroom 4.3. Center: Mid-left-lower: Mid-right-upper: Left edge: Right edge: Far-upper-left: Far-lower-left: Far-lower-right: As evident from the files, color fringing correction, while easy to do in Lightroom, was not applied. Barrel distortion has been corrected in Lightroom, which robs the image of some sharpness. Also remember that depth of field (DOF) will affect this kind of test. For example, the proximal corners are outside the DOF at the low f-numbers. The right edge crop shows that my lens has some decentering (lens elements are not perfectly centered, so one edge is sharper than the other). This is true for most lenses, and I consider my copy of the lens to be within specifications (not defective) in this regard. It's no different than most lenses I've bought over the years.