the idea of 'perceptual image structure'
Seems like most here are pushing for establishing subjective stances and not basing them on graphs
I'll take these together as they aim at the same point. In essence, resolution tests are a profoundly incomplete measure of how a film performs in the real world (in fact, even when well done, they tell you little that the MTF can't (you can forecast the results accurately if you know the test chart contrast), other than the tester's errors - e.g. in reading out at one MTF for neg films, and another for transparency - which renders the result perplexing to the mk.1 eyeball, even if the numbers are nominally 'correct') - especially compared to how using the materials in question under tightly experimentally controlled & demanding real-world scenarios can often (if done well) allow for close linkage to the much more useful MTF/ RMS granularity information which does much more to define (along with usable latitude) the ability of a given material to capture and transmit information. However, some people (usually outside of the industry) try to link up MTF to outright resolution in order to play the usual zero-sum games, rather than ever linking back to double blind tests at an array of enlargements (which of course must be done with optimised lenses, such that they don't overly influence the result). Spectral sensitivity tests also can tell some of the story, but seem rarely done (in the popular press/ influencer world) to normalise for all the potential variables. In other words, do some basic & sensible tests, but unless you can produce exceptionally well controlled data, you are never going to get close to the manufacturers (and this applies to the home developer formulators in particular - they are often unknowingly reliant on the manufacturers successfully compensating for potential end user error) test results - which I wish they were sometimes more willing to share in more detail, as it might clear up a lot of fashionable nonsense.
Anyway, even a 3x enlargement off 120 will show up the K400/ HP5+/ Delta differences - the low frequency response is clearly one of the biggest areas of difference.
Instead, they are coated on a grey base, which absorbs light twice, providing most of the anti-halation that is needed.
This is rather inaccurate - only a few rely entirely on the grey/ dyed base (usually the budget options) - many also incorporate anti-halation within the emulsions/ layer structure and/or as discrete layers (e.g. Agfapan APX 100 and successors have a discrete anti-halation layer). The grey base is almost more about preventing light-piping effects than acting as a complete anti-halation solution on many emulsions. A lack of strong anti-halation protection within a multilayer emulsion structure can become very apparent in the highlights with overexposure e.g. K400, Fomapan 400). C-41 emulsions incorporate both a discreet anti-halation layer and anti-halation within the emulsion structure as the base of C-41 is clear and would otherwise light-pipe terribly - and within the emulsion layers further anti-halation is essential as you would otherwise get each layer behaving like a mirror.
Kentmere reminds me very much of 1970s Tri-X.
It is especially nice in 120..
Sort of - but it can also look like a bit less sharp version of a more 'modern' Delta style film too (for the record Delta 400 has a very similar curve to TX) at some points in the frequency response. Overall, something of a hybrid in some areas (which would probably have been ironed out if it was to have been a premium emulsion).
