I need some guidance. I bought the Mamiya-Sekor Macro C 80/4 lens today. I downloaded the manual for this lens and it talks about using the Macro Spacer to obtain 1:1 magnification. Without it you can get 1:2 magnification. There is a setting on the lens that needs to be set appropriately for using and not using the Macro Spacer. Now here's my question. I already have a set of 3 genuine Mamiya Auto-Extention Rings (1,2 & 3). Ring #3 looks to be about the same length as the Macro Spacer pictured in the lens manual. Does anyone know whether the macro spacer and these auto-extention rings are interchangeable? And if so, do I set the selector switch on the lens the same way?