Beamer Font Size for Footer

Question

How can I change the font size of the footer in Beamer without modifying the font of the title (on the title page)? Also, when I try to change the title's font with \title{\fontsize{20}{25} My Title} it doesn't seem to work. Thank you.

Answer 1

You need the command \selectfont after fontsize

\documentclass{beamer}
\usetheme{AnnArbor}
\title[My Title]{ \fontsize{20}{25}\selectfont My Title} 
\begin{document}
\frame{\titlepage}
\frame{a frame}
\end{document}

Detailed information are documented in the Docmentation of LaTeX font commands

EDIT: Use the theme AnnArbor and the optional argument of \title.

Answer 2

You can change the font for all the elements in the footline simply by setting the footline font using

\setbeamerfont{footline}{size=<size>}

A little example:

\documentclass{beamer}
\usetheme{AnnArbor}

\title[Short title]{Long}
\author[Short author]{Long}
\institute[Short inst.]{Long}

\setbeamerfont{footline}{size=\fontsize{9}{11}\selectfont}

\begin{document}

\begin{frame}
\maketitle
\end{frame}

\end{document}

Of course, if the chosen font is too big, the results obtained won't be very pleasing (try using \fontsize{10}{12}\selectfont in my example code above). In this case, you will have to change the footline template. In the following example I made some changes in the spacing between the date and the page number and after the page number, to have a footline with a font size of 10pt:

\documentclass{beamer}
\usetheme{AnnArbor}

\title[Short title]{Long title}
\author[Short author]{Long author}
\institute[Short inst.]{Long institute}

\makeatletter
\setbeamertemplate{footline}
{
  \leavevmode%
  \hbox{\fontsize{11}{13}\selectfont%
  \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=1ex,center]{author in head/foot}%
    \usebeamerfont{author in head/foot}\insertshortauthor~~\beamer@ifempty{\insertshortinstitute}{}{(\insertshortinstitute)}
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=1ex,center]{title in head/foot}%
    \usebeamerfont{title in head/foot}\insertshorttitle
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=1ex,right]{date in head/foot}%
    \usebeamerfont{date in head/foot}\insertshortdate{}\hspace*{1em}% original: 2ex
    \insertframenumber{} / \inserttotalframenumber\hspace*{1ex}% original: 2ex
  \end{beamercolorbox}}%
  \vskip0pt%
}
\makeatother

\setbeamerfont{footline}{size=\fontsize{10}{11}\selectfont}

\begin{document}

\begin{frame}
\maketitle
\end{frame}

\end{document}