Long time reader / first time poster. I recently purchased the 24-105mm lens as an upgrade of my 28-135 lens. From the reviews I have read, it appears the 24-105's performance at 105mm is not as strong as other focal lengths. When I shoot at relatively close distances at 105mm with my 24-105mm lens using the center focus point, the center performance of the lens appears fine but the corners appear out of focus rather than merely soft. I've looked at images from distances between 10-30 feet and noticed the same results. The corner performance at 105mm with subjects at or near infinity focus is fine (about the same as my 28-135mm but not as good as my 70-300L, which is about what I expected). Perhaps the increased depth of field at infinity focus explains this. Stopping down to F/8 also helps, but does not completely alleviate the issue. Applying an AF microadjustment of +10 on my 5D III improves corner performance; however, the center performance then deteriorates - the same also happens when I focus on the corner of the frame either through live view or the viewfinder. As all the corners are out of focus to approximately the same degree, this does not seem to be a centering issue. Has anyone else experienced this with your 24-105mm lens? Is this typical behavior for the 24-105mm lens? Thank you in advance for your comments.