Tom Hicks wrote
Get an old minolta, pentax, nikon, takamar, manual focus lens , set f stop , and simply hold it up to the camera body and take a few shots of a static object and see what you get it's that easy . you can use your 60 macro , set f stop , Mash DOF preview button,while removing the lens from the camera and it will stay fixed at that f stop , rev and hold to body face , put camera in AV mode meter and take the shot.
.
Thanks for this Tom. Utter genius! Works a treat with my 50mm 1.8 mk1. Having fun. Results later.
Paul