Why do some fonts used by siunitx and textcomp look rasterized?

Question

For example, the mu in \SI{1.55}{\micro\metre} looks really bad for some reason. For textcomp, \textmu looks the same.

Answer 1

Turning Ulrike Fischer's comment into an answer: This happens because you are using the type 3 versions of the TS1 encoded fonts that are accessed via the textcomp package. There are 2 simple ways to resolve this.

• Install the cm-super fonts, via whichever mechanism your TeX distribution allows (these fonts are very standard and should be available for every major TeX distribution, but since they are quite large they are not always installed by default).
• Put \usepackage{lmodern} in the document preamble, to use the Latin Modern fonts.

Both of these options should fix the problem of using type 3 symbols, and should have only very minor effects on the rest of the document. The first option should only change the problematic glyphs; the second option will also cause very slight changes to the whole document (you may or may not view these as improvements, or you may not even notice since the difference is very subtle).

See Latin Modern vs cm-super? for some tips on the difference between lmodern and cm-super.

See Finding ‘8-bit’ Type 1 fonts on the UK TUG FAQ for some more background.