There are some RF lenses that go down to 70cm, besides the DR 'Cron that is M-mount only.
But also check your rangefinder can go that close, some bodies only go to 1m as well. Easiest way to tell is to take the lens off so the RF cam springs out, then move the camera until it's focussed on something and measure how far away that it. Then don't forget the parallax errors that you're going to get.
There are some things that SLRs are just way better at than RFs, and macro is top of the list.