Neat, but this completely ignores the real reason people have trouble with small fonts: bad eyesight. The size the font needs to be is a factor of distance and eyesight. The real solution is to just use the default font size and have users adjust that to their preferences.
and the ambient light conditions, the amount of sleep someone has had, color blindness (could be classified as bad eyesight), the actual size of the screen (for scrolling/line length), the font itself, the amount of experience the reader has with the latin script, the quality of font hinting, the quality of sub-pixel rendering, the quality of kerning.
I wonder if, with a good enough camera, you could detect people with non-ideal vision by watching their eyes and "anti-blur" the screen in such a way that it's perfectly in focus for their eyes and head position?
This is a really interesting thought! It's something that probably wasn't viable before the advent of High-DPI displays. Making it worth the effort in a real-world (rather than lab-based) setting is probably insanely difficult though.
