Is there such a thing as optimum shooting distance for a given sensor, lens, focal length and aperture e.g. if photographing an object 75mm high at a distance to subject of 30 metres using a focal length of 300mm, is it reasonable to expect a sharp image when cropped to fill an image size suitable for AP given appropriate shutter speed (fast) and use of a tripod/monopod.

Am I expecting too much of a camera/lens system to produce acceptably sharp images with the above parameters? I realise there are probably a lot of other variables such as glass quality but I am continually amazed at the high quality of the images appearing here but there is no distance to subject info disclosed?