....Resolution in film is a measure of how DEEP the layers of grains are stacked and how much absorbing dye can be introduced to prevent internal reflections of the light. In other words, scatter caused by turbidity is your problem in limiting resolution.
Ah-ha. Light dawns on Marble Head.
This is why the flat T grains are so much finer detail? Do I understand this now? Or at least begin to do so?
Well, yes. AgX is more or less transparent and is then sensitized by coloring it with a sensitizing dye that is the opposite color of the light it is to absorb. Thus red light goes through a green sensitive t-grain pretty much. But remember that a pan sensitized t-grain is gray or black and therefore absorbs light.
So the answer is different depending on how the emulsion was dyed and whether it is B&W or Color.
I always though that the appearance of grain in positive photographs is a map of the spaces between the grains of the negative. Ok, smaller negative grains make for smaller spaces but the spacing is also influenced by the number of negative grains per unit area. A dense part of a negative has fewer widely spaced "gaps between the grains" so the ability of dense parts of the negative to carry detail and gradation information is reduced.
Trying to come up with a single number to compare negative grains or more realistically the spaces between them with pixels may be a lost cause.
Photography, the word itself, invented and defined by its author Sir John.F.W.Herschel, 14 March 1839 at the Royal Society, Somerset House, London. Quote "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..". unquote.
My personal experience is this: when comparing my film scans (Nikon Super Coolscan 5000 ED used at its maximum 4000 ppi resolution, 16 passes each slide, 2 exposures each slide, minimal ICE scratch removal) of E-6 slide films with my 10.8 mp digital camera (Sony DSC-R1) I can see a clear advantage of the film scans compared to the digital captures, as far as resolution is concerned. Digital captures appear "cleaner" but they do have less details.
With my setup the equivalence would probably be around 20-30 mp. If comparing with a better scanning procedure ("wet" drum scanning) the equivalence would very probably be at a higher pixel count but costs would rise quite a lot.
To me digital has its advantage in being more versatile (not just faster workflow, but also the possibility to change ISO setting on the fly, which can be quite precious) and film has its advantage especially in the superior dynamic range. Slide scans behave much better than digital IMO under this respect. It goes without saying that negative colour film is even better and by a long shot.
I will not dwell into different pros and cons between digital and film to avoid being boring and off-topic.