Hi,

I would like to trying some macro photography with my Mamiya RZ67 using a 110mm lens on the body and a 180mm lens reversed in front of this. I've got a double threaded coupling ring but I can't work out how to calculated the exposure using a handheld meter when you have the two lens mounted on the camera.

Can anyone offer an explanation of the corrections needed to allow for the second lens mounted on the front?

Thanks