This is if you measure real sharpness instead of acutance (which latter is strongly affected by those edge effects). XTOL stock or 1+1 delivers the highest resolution and real sharpness with all or almost all modern film stocks, and will be in top three developers for the old school (like Fomapan 100 or 400) -- but it shows almost no edge effect with continuous, 30 second, or 60 second agitation cycles. Dilute Rodinal has distinct edge effects, as do developers like D-23 1+1 or 1+3, or D-76 1+3.
I think you're confusing coarser visual granularity with greater edge effects (a very commonplace error). It also (unintentionally) actively denies the existence of a vast chunk of imaging science work post-1950ish that has informed all the big manufacturers products at the most fundamental levels.
Kodak (and everyone else) was/are measuring edge effects using microdensitometry (and double blind visual analysis too) and there is clear evidence (backed up by Richard Henry's work) that even stock D-76 is as good as Rodinal for edge acutance/ sharpness, but Rodinal has much coarser granularity (which limits information transmittance at high frequencies). Some of the answers seem to lie in the bell curve plot that describes pH against edge density - which peaks about 10 and where D-76 and Rodinal lie almost parallel. Neither D-23 nor D-76 will produce edge effects from their developing agents alone - too concentrated in D-23 for exhaustion effects, and the HQ in D-76 (effectively HQMS) acts against Metol exhaustion effects (PQ is different) - the adjacency effects they have are from the solvency of the sulphite acting on the emulsions, releasing byproducts (Iodide, some Bromide, and other possible addenda). Having made 40x enlargements off negs developed in D-76 (with appropriate enlarging lenses and well damped / braces enlarger), I can definitely say that the grain off D-76 is not unsharp, but it is quite fine. Things like Ilfosol 3 ramp up the adjacency effects, so while the granularity size difference with D-76 is not much different, it is more visible, grade for grade. The claims about Rodinal etc date from the era of inefficient polydisperse emulsions with the iodide buried in the structure - as opposed to the much more controlled emulsion structures that emerged from the mid 1950s onwards. And Kodak, Ilford etc could have made Rodinal easily (and probably more cheaply) - but they chose not to, for good scientific reasons. Rodinal's survival probably owed more to it fitting the same niche that amateur/ hand-line small in-house labs were using HC-110 single shot for (and the fact that Agfa's attempt at an HC-110 was called Rodinal Spezial in some markets suggests that Agfa was pretty aware of this) - an exotic product that had acquired a (frankly rather bizarre at this distance) cachet as a fine-art silver bullet that was relatively cheap single-shot and had immense life expectancy as a concentrate.
www.photrio.com
