David HB, rodinal, as I know do not cut film speed. The most pronounced characterstic of rodinal is high acutance. This can be reason that grain, in high speed films, might be looks larger when processed in rodinal. They are actually not larger just more visible.
Pan-F in Rodinal has iso64 (my two batches), Delta100 my present batch is iso100, previous two were iso125 and iso160, HP5+ once had iso650 and iso400 next batch, Delta3200 was iso1200
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Rodinal (and like) is the best choice for high quality lenses like Leica, some Nikkors, Zeiss, Schneider, Rodenstock,.... and is not the best for soft lenses (like lenses for female portraiture, or Nikkor 1.4/85AF used at F1.4 to F2) or when softar is used... It is very good choice for very fine details in shades especialy for smaller formats as 35mm and 56x56mm (like Hasselblad).
Development time however a lot depends of water used for developer, its ph value and all of that chemicals found in. Only destiled and boiled water has around ph7. I use tap water and development time may considerably differ from time in other region. But I found that for grade 2 paper (ilford), condenser enlarger (that I use mostly) developing time is very different then what ilford offer (and agfa too). Time for Delta100 is 7min and 45 sec with rodinal 1:50 at 20 deg.C and agitation each min for 10 sec. Film speed (working) can also be different for different lenses too for e.g. F5.6 is not the same aperture area on different lenses, and difference go up to +/- 1/3 F stop even for the same manufacturer. So to properly expose the film to get max out of it req. is also that one knows his lenses and camera (shutter also has deviations form camera to camera, even more than F stops).
The best for Delta3200, for blind guess, is to set meter on iso 1200 for daylight, and iso iso1000 for artificial light (around 3200 K) as domestic light bulb is, or for street night photography. Rodinal is not bad choice because that films are usually used for dramatic scenes and large grain will add drama due to mysterious appearance of the grains on the photos. Rodinal should be 1:25 and as I just can remember this moment the time is around 12 min (not 100% sure) at 20 deg.C. In 1:50 time is very long (around twice).
I will get for tomorow exact developing time for Delta3200 I use (not promising), and will update THIS post.