There is simply too much conflicting information being spread about R09 dilutions. I recently posted a question about converting Rodinal to R09 dilutions on Photo.net
http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00Bsvq and much of the information is in crass contrast to what is being proferred here as fact.
I am taking the liberty of posting here my latest contribution to the above mentioned thread. Hopefully, this will be of value and generate some insight.
Regarding the seemingly factual statement that R09 is more concentrated than Rodinal, everything I have found published, including the ORWO film processing chart
http://www.digitaltruth.com/chart/old/orwo_old.html which compares R. and R09 suggest otherwise.
Now, I am the first person to say that empirical testing is the ONLY real way to discover truth. Even well meaning advice can be tremendously misleading when one considers variables such as enlarger variations, paper, film, agitation and so on. Not to mention that we all find different ideals in contrast. This last factor -- the subjective nature of judging ideal negatives can't be underestimated. Still, sharing experience and knowledge is often helpful and interesting.
Now... here's where it gets interesting: in ORWO's own "Developer R09 - Directions for use" the suggested time for NP15 (IS0 25) is "approx. 9 min." @ 20 deg. C. in a 1:40 dilution. Then... ORWO suggests a Multiplying Factor of 1.5 for 1:60, 2 for 1:80, 3 for 1:100, 4 for 150 and 6 for 1:200.
Based on their suggested 9 minutes at 1:40, using a 1:150 dilution would require 36 minutes for Efke 25!
Obviously, I plan to test this -- arghhh! -- in the darkroom, but I thought this was intersting information considering the 20 minutes time that seems to accepted by most here in this thread. Remember, using Ronald Moravec's and others theory of a 1.6 factor difference betoween R. and R09, the 1:150 dilution would be close to the 1:100 Rodinal dilution.
APUGERS, HELP! There must be some definitive information out there.