[Tex/LaTex] The caption package and letterspacing

captionsletterspacingmicrotypesmall-caps

Problem Statement

I adjusted the caption format for my figures and tables using the caption package, such that the words "Figure" and "Table" are typeset using small caps. Now I want to obtain correct letterspacing for these words using the microtype package and the command \textls, but adding labelfont = ls in the caption setup doesn't work.

Minimal working example

\documentclass{scrartcl}
\pagestyle{empty}
\usepackage{tikz}
\usepackage{microtype}
\usepackage{caption}
\captionsetup{
    format = plain,
    font = footnotesize,
    labelfont = sc
}
\begin{document}
\begin{figure}[!htb]
    \centering
    \begin{tikzpicture}
        \draw (0,0) circle[radius=1];
    \end{tikzpicture}
    \caption{A circle.}
    \label{fig:sine}
\end{figure}
\end{document}

Sample output

caption

Note the non-letterspaced small caps here.

Best Answer

The KOMA-script classes have their own method for changing basic aspects of the caption typesetting. On the other hand, the caption package allows greater flexibility and many more customization options.

Since the package can't know each and every font combination, it also provide an interface for defining new options.

In your case you can do

\usepackage{microtype}
\usepackage{caption}
\DeclareCaptionFont{ls}{\lsstyle} % define a new option

\captionsetup{
  format = plain,
  font = footnotesize,
  labelfont = {sc,ls},
}

See Section 4 “Own enhancements” in the documentation of caption.

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