We need more clarity to help with this problem. For example: you put the 50mm lens on and point it at a subject 1 meter away. Now you turn the focusing ring to bring the subject into focus:
- are you looking at the focus indicator, or focusing a sharp image on the focusing screen?
- do you mean that when the image (of this subject at 1m) on the focusing screen is sharp, the lens focus ring scale is at infinity?
- or that when you turn the focusing ring to 1m, the focusing screen shows a sharp image at infinity?
Problems like this sometimes mean that the mirror or focusing screen is out of place, or the lens mount is out of place (or even that there's a diopter on the eyepiece, although that would make everything blurry including the viewfinder readouts). Pictures of the camera lens mount and mirror/screen area also may help.