When mounting a ‘mechanical’ adapter, that is one that has no electronic connection, the camera does not recognise that an adapter is attached, even if a lens is mounted on it. The Canon EOS R5 is delivered from the factory with the option to operate mechanically adapted lenses disabled (as are other EOS R cameras). No doubt this is to protect the shutter blades and sensor, but it means you will have to enable the option, which Canon describes as ‘release shutter without a lens attached’. This presumably refers to operating the camera to check the shutter operation, but more often than not, I suspect users are going to want…