EFS 17-55 USM corner blurriness: experts' opinion needed !

70d IF wrote:

A few customers will complain and they will repair their equipment.

The problem is that I've personally never had a decentered lens that a repair centre was able to properly repair. In fact some lenses seem to have zero adjustment capabilities other than to replace the molded parts the elements sit on. So far only exchanging the defective lens has been effective, but the hassle is so annoying (especially when they tell you that it's "within manufacturing tolerances") that I've started to do what I didn't want to do : I buy online several copies and only keep one, if there is at least one that isn't badly made.

I've heard some positive stories regarding a service centre ability to repair decentered lenses, mainly from Canon, but having to send a lens for repairing a decentered element remains one of the things I dread most (with sensor / AF module / mount hardware and software calibration).

Interestingly decentering seem to come in batch from my experience. I've had massive issues with Olympus recently, and out of seven 25mm I tested, only three weren't decentered to a significant degree, the other four had a tilted focal plane (or sphere, if you want to take into account field curvature), much closer on the left side, with some variation, sometimes rather the lower left side, sometimes the upper left side, but always closer on the left (note : the bodies were fine). All the defective ones had earlier serial numbers, all the good ones later numbers. BTW, Olympus service has been utter rubbish, in fact they managed to go straight to my personal top 1 of the worst customer service I've ever had in my (short) life.