Originally Posted by
Diane Miller
Anita, are you using a tripod? With macro, you can focus precisely on a desired spot, but if you are handholding and you inadvertently rock slightly back and forth while holding the shutter button down for a split-second (after focus is locked) you can move that object out of the focal plane and it will be soft.
It is also possible that the lens is not well-enough focus calibrated with the camera body. If you have Live View you can zoom in and focus by what you see on the back screen, and you are bypassing the focus sensor. Not always practical but its a good way to check autofocus accuracy.