This is an interesting discussion. I've always assumed that there is a correlation between edge effects and agitation ; i.e. the less agitation, the more pronounced the edge effects, as the layer of bromide at the edge of high density areas is removed by agitation - this just seems commonsense. Now I'm wondering whether this really is the case, although I have certainly noticed differences in films where I have extended the development time and reduced agitation in order to try to induce edge effects. Different film emulsions will probably behave in different ways in this respect.(posted 8447 days ago)John - you haven't mentioned temperature in all your tests above, probably because you have ensured it is consistent between the various tests, but I'm wondering if this could be one factor involved in producing the development time differences you have found. Could you please comment if only to eliminate this as a possible factor?