NOTE---->If the image on the film plane is out, the screen height can be adjusted to bring it in focus with the taker lens. Sometimes the viewing lens/ viewing screen, is slightly out of adjustment... but only do this if ALL your lenses are out of focus. If this is the only lens doing this, then the viewing lens or taker lens needs to be adjusted.
Sometimes people install bright screens which are focused to the camera. Then when the camera is sold they pop in the old screen without readjusting the focus.