When I was about 13, having exhausted the limits of my Kodak Pocket Junior camera (a 120 roll-film, fixed-focus folder with a single-element lens and two shutter speeds), I pestered my father for a "real" camera until he gave in. I left the camera store the proud owner of a 2 1/4 x 2 1/4 Korelle Reflex I SLR with speeds from 1/25 to 1/500 sec, an interchangeable 75mm f/3.5 Ludwig-Dresden Victar lens, and a Weston 650 lightmeter.
My father explained that the further I closed down the aperture, the sharper the picture would be. At f/3.5, the lens was barely sharp enough at the image center; edges and corners were less so. Stopping the lens down to about f/11 provided adequate central sharpness, and it improved the corners somewhat.
Too many importers of even quality products skimp on their repair facilities or personnel. Repair could be a profitable item, but selling cameras is more so. Many a conscientious importer or manufacturer might indeed wish to have the very best repair but probably can’t get the technicians. Good camera technicians are no more scarce than good automobile mechanics and any garage owner can tell you how darn hard they are to come by. 
