Maybe I will learn something new here.
I honestly thought that all chemical reactions slowed down with a developer/film combination that required long development. Take, for example, D-23 with Tri-X at 68F: it takes 'forever' to achieve adequate contrast. So, I thought logically, that agitation with that combination should be about every two or three minutes, with a total development time of 20 to 30 minutes. Or take HC-110 using a rather active dilution of 'B', with Pan F: Maybe less than five minutes, total, would be adequate for such development (achieving same gamma), and, with that combination, agitation at least every 30 seconds would become mandatory for complete freedom from possible inconsistency.
kintatsu posits that separation between high and low values is decreased with less agitation. That is true in an absolute sense, of course, but not necessarily true in the two relative senses I pose above. With long, long development times I don't think that 'every 30 seconds' achieves any greater separation than with 'every two or three minutes'. Why? Because with slow development the developer reducing the highlight area remains just as strong as the developer reducing the less taxing shadow areas for a lot longer time. Thus, there is no exhausted developer to replace (yet). But with the fast development for Pan F and HC-110, the exhaustion takes place far more rapidly, thus agitaion must be far more frequent.
Regardless, maybe I am incorrect; your diverging viewpoints are certainly welcomed. Sometimes that which seems logical proves to be misguided when others offer better reasons. - David Lyga
Last edited by David Lyga; 04-12-2013 at 04:36 PM. Click to view previous post history.