Earl Dunbar said:
The market for slow, small format film is really small. That, I fear is the bottom line. Yes, modern emulsions are often as good or better than slower films of old. But with the advances made, it would be interesting to see someone take a whack at a great panchromatic 25 speed film.
I understand your desire for the improvement, but I see a very good reason why no one wants to make an extremely fine grained b&w film at 25 speed.
The last major increase in speed-to-grain ratio happened in 1990s. (Another technology, called two electron sensitization is beginning to be used in commercial products, which further doubles the speed of emulsions of same grain size.) At that point, they could make a 100-speed b&w film that exceeds the resolution of good, fixed focal-length lenses for 35mm format, and the grain could be already very fine. Fuji Acros and Kodak TMX are two films that give this level of excellent resolution, both with excellent fine grain and reciprocity failure properties. Since most people use zoom lenses, or shoot with suboptimal conditions (handholding, mirror vibration, film flatness issue, etc.), there is really no need for films to increase the resolution any further, unless there is a revolution in optical design. Color films, on the ohter hand, are always inferior to b&w films of the same speed in terms of resolution. Indeed, crystal sizes used in color emulsions are much larger than b&w of the same speed. So there is still lots of desire for color emulsions to improve.
If there's any problem in this design spec issue, the camera optics are usually designed to meet the resolution of slow color films. When people argue the equivalent megapixels of 35mm format, they are of course assuming the typical MTF characteristics of a slow color film.
So, as David said earlier, I also think using a bigger format is the real solution for improved image quality.
My desire goes to more variety in enlarging papers... I think we have enough films.