He speaketh a great and noble truth! Dang, you learn something every day if you surround yourself with smarter folks.
Originally Posted by mwdake
I think the mask may be built in; you may want to check. I have the same camera and the mask is 2 little leaves in film gate that fold over for 645 and fold in to the spool area for 6x6.
The little switch next to the viewfinder switches the viewfinder from 6x6 to 645.