Donald Qualls
Subscriber
I've used Rodinal at 1:100 for microfilms and got useful grayscale. Not the rich tonality of an ISO 100 conventional film, but definitely a range of gray. I don't recall the time I used, but most likely I used my usual 3 minute agitation cycle, which improves film speed (compared to same developer in conventional agitation) while keeping contrast from blowing out.