But 150 ml figure was arrived at for the benefit penny pinching commercial processes that wanted to use the bare minimum to achieve semi-acceptable results. But what was forgotten, according to Anchell,was that the Kodak research showed that much better results would had by using 250 ml of developer per roll
I think you're very confused about this. First, the figure of merit here (for Xtol) was 100 ml, not 150; second, this was Kodak's research, intended to tell the minimum that would
meet Kodak standards for negative quality. Not the "least you can get away with", but the minimum that would produce negatives Kodak (the old Kodak, before the film market crashed) was willing to put their name behind. Third, those "penny-pinching commercial processes" never used diluted developers; they ran replenished, which uses just 70ml of developer as replenisher after each 8x10 equivalent has been processed, while developing in full stock strength developer. Replenishment is by far the cheapest way to run a high volume development line -- not just in developer capacity, but in time as well. It takes much longer to process film in dilute developer than in stock strength solution, and in high volume commercial processing time is a significant consideration -- most film through the system = most money taken in for the same overhead and wage costs.
The other side of this, however, is that by the time Kodak introduced Xtol (1996), black and white commercial processing was no longer a high volume business. It was significantly harder to find a place that would develop your B&W film in house at all than to get color negative film processed with prints in your hand inside an hour. Xtol was, realistically, introduced for the professional photographer who did his or her own film processing and printing in black and white -- a breed that, for economical purposes, virtually vanished over the following ten years.
Those are the workers who might, because of the change in character of the negatives, prefer to process in diluted developer and need to know that they were risking having their contrast index vary with the level of exposure of the negative if they used less than 100ml of stock for an 8x10 equivalent, regardless of the dilution (meaning 1+1 was fine, but 1+2 might not be for 35mm or 200 -- but would be for single loaded 120, different because of the ratio of film to solution). These are the same workers for whom Kodak had published this same information going as far back as the introduction of D-72 (commercially sold as Dektol) and D-76 before WWII.
