“Micro-Typographic Extensions to the TeX Typesetting System”, 2000-10-01 (; backlinks; similar):
This thesis investigates the possibility to improve the quality of text composition [using microtypography]. 2 typographic extensions were examined: margin kerning and composing with font expansion.
Margin kerning is the adjustments of the characters at the margins of a typeset text. A simplified employment of margin kerning is hanging punctuation. Margin kerning is needed for optical alignment of the margins of a typeset text, because mechanical justification of the margins makes them look rather ragged. Some characters can make a line appear shorter to the human eye than others. Shifting such characters by an appropriate amount into the margins would greatly improve the appearance of a typeset text.
Composing with font expansion is the method to use a wider or narrower variant of a font to make interword spacing more even. A font in a loose line can be substituted by a wider variant so the interword spaces are stretched by a smaller amount. Similarly, a font in a tight line can be replaced by a narrower variant to reduce the amount that the interword spaces are shrunk by. There is certainly potential danger of font distortion when using such manipulations, thus they must be used with extreme care. The potential to adjust a line width by font expansion can be taken into consideration while a paragraph is being broken into lines, in order to choose better breakpoints.
These typographic extensions were implemented in pdfTeX, a derivation of TeX.
Many experiments have been done to examine the influence of the extensions on the quality of typesetting. The extensions turned out to noticeably improve the appearance of a typeset text. A number of ‘real-world’ documents have been typeset using these typographic extensions, including this thesis.