That's interesting, because it's not been my experience (which is limited of course) to be true. For example, all camera films I have used/tested have had Dmax around 3.0 but have tested only 3 developers all giving nearly the same, but those are similar developers. With ortho litho film. with Dmax of 4.5, I can get no more from that with E72 print developer than I can with D23, it just takes more time. The Dmax is critical to know for reversal processing, since it helps us to know how much fixer to add in the developer for roll film, or how much to flash the film for density range control of sheet film.
My measured density for HRU base is 0.283. I've not been subtracting this out from density reports, as I should. This lowers my measured density on that negative I showed from 1.89 to 1.61 and from the clip test from 2.2 to 1.91. Andrew O'Neale did a video recently where he did characteristic curves for this film, and was getting Dmax of about 1.85, which is in line with what I see. I was surprised it was so low, and texted a question on developer exhaustion. I think that's about all there is with this film when used directly for contact prints. Higher contrast would not work in this case due to shorter exposure range. For enlarged negatives via reversal processing, higher energy developer would work, but this would likely require original negatives that are much more contrasty than most. A little disappointing.
