I've primarily been using Delta-400 and D-76 1+1 for the past few years (35mm) enlarging up to 11X14 and wanted to start trying some Rodinal. I developed a test roll of bracketed exposures of the Delta in Rodinal 1+50 for 19 minutes and the results timing wise were right on with the negatives looking real nice under a loupe. I have yet to enlarge a negative. I will soon try some tests with Tri-X and HP-5. My questions are what differences do you get with different dilutions as to grain,contrast,tonality etc.. I see people using 1+25 up to 1+200 and am interested as to why.