# Subscript scaling with Latin Modern Math

I'm using XeLateX, Unicode math, and the Latin Modern fonts (Latin Modern and Latin Modern Math). To me, it looks like subscripts in mathematical expressions are being properly (optically) scaled -- they are not merely small-size versions of regular characters, they are wider and have fatter strokes.

Here's some code

\documentclass{article}
\usepackage{unicode-math}
\setmainfont{Latin Modern Roman}
\setmathfont{Latin Modern Math}
\begin{document}
Here is some math: $x_2=2$.
\end{document}


and the output

In traditional TeX, the subscript scaling would be done by using a completely different font, like cmmi7. But the Latin Modern Math font only comes in one design size (10 pt, I suppose). So how is the subscript scaling achieved?

In OpenType math fonts, the optically scaled glyphs for script and script script sizes are included in the same font file (usually ununcoded) and are mapped using ssty feature, which unicode-math enables as appropriate.
• In XeTeX you can use \XeTeXglyph to access any glyph in the font (encoded or otherwise) by its index. – Khaled Hosny Nov 10 '14 at 18:07