I’m trying to figure out how to do a paper microprint system for my notebook.
If I print text out at a line height of six 600dpi pixels, it’s like uh 100 lines per inch so 0.72 point. For text to be comfortably readable with the naked eye it needs to be 12-point, which is the standard line-printer 6 lines per inch; that’s 16⅔× bigger. So a head-mounted magnifying apparatus of between 16× and 30× is probably adequate to make it comfortably readable.
The column width shouldn’t be more than about 0.3 radians in order to be comfortably readable. At 30×, an apparent 0.3 radian image is something that was originally 0.01 radians; this means that if it’s at a distance of 500mm (from the lens), the column width is then 5mm, which is 118 pixels at 600dpi; at 3.5 pixels per character, that’s only 33 characters, about 6 words. So being towards the lower end of that range is probably desirable for ergonomic reasons.
4.8× handsfree magnifying visors are readily available, but 15× and 30× are harder. I did find a 20× one with LED illuminators and a 10× monocle one each for about US$27.
If we stick to 10×, we want 1.2-point fonts, which are 10 pixels high on a laser printer, or maybe 8 or 9 pixels with 1 or 2 pixels of leading. If the glyphs occupy 5 pixels horizontally, then a 600×600 pixel square inch can contain 7200 characters of text, or about 1440 words; a 4×5 inch A6-size page with some margins can hold twenty times that, 144 kilobytes, 28800 words or about 27 standard line-printer pages. Call it 32, then 16 pages (8 sheets of paper) holds 512 standard pages.
(There’s still the unknown of whether I can properly align the pixel grids and fully exploit the 600dpi theoretical capability of the printer, or whether I have to stick to Nyquist, taking a 4× areal density hit.)
Some ideas of what to put in it:
http://piratepad.net/4e311Fk9yz