Thanks for the help, guys. I tried a little microadjusting, and I think it may have solved the problem. Didn't have a whole lot of time to set up proper lighting or anything, but just from a quick test, the problem was apparent.


This is the lens prior to adjusting, at 18mm, from about 8 feet away:


[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.30.41/zero.jpg[/img]


This is the adjustment at +10:


[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.30.41/plus10.jpg[/img]


(Glad I finally found a use for the bizarre, shiny string my girlfriend has lying around)


The problem is only apparent at wider focal lengths. Is that normal for this kind of problem? I've had this lens for a while, but most of my shots are around 40-55mm, so it took me a while to really notice the focusing problems. I also bought this lens refurbished. I figured that a refurbished lens would've been put through its paces, since it had to be repaired anyway, but I guess I should've checked it out better.


Anyway, thanks again everyone for the suggestions. I'll have to do more tweaking, but I think this is the right track. I can't thank you guys enough. I was really going crazy over this.