Hi there, new member here. Regarding sharpness of image issues with DX cameras and lenses, certain Nikon cameras do not, of course, have the in-built calibration function. If, like me, you are the owner of a Nikon camera that does not have the in-built sharpness calibration function, you are left to find a methodicity to gaining acceptable sharpness in your images.
When I first started taking photos with the D5000, I found many of the images were softly focussed, and soon became annoyed with it. There was nothing wrong with the camera, or the lenses I was using, it was my picture-taking method, but it was a voyage of discovery that led me to this conclusion.
I tend to shoot a lot of hand-held shots, even for the landscapes, but having invested in a tripod, I started to see some improvement.
If, when using a tripod, for say the D5000, ensure you use the 'delayed exposure' function (to dampen mirror movement), and turn 'VR' off on your lens. Also, invest in the remote control for your particular camera, as using your finger to press the shutter release can induce vibrations, even when the camera is mounted on a tripod.
Another issue with the D5000 is to use the correct or optimal aperture setting, try not use anything smaller than F11, and focus at a point about a third of the way into the scene from the camera. Smaller apertures than F11 can often bring about soft focus issues due to diffraction.
I guess the point I am making is to firstly eliminate errors in your picture-taking method before placing blame on any of your equipment. It will help to save time and inconvenience of returning items back to store or manufacturer. I should also think that the little tricks I have outlined here in my post are already known by you guys?