Beamer Section Titles with Shortened Titles in Top Bar of Slides

Question

I would like to have multiple slides with a titles for sections that place the title of the section in a box similar to the main title for the slides. @gonzalomedina helped by recommending the code:

\documentclass{beamer}
\usetheme{Madrid}

\AtBeginSection[]{
  \begin{frame}
  \vfill
  \centering
  \begin{beamercolorbox}[sep=8pt,center,shadow=true,rounded=true]{title}
    \usebeamerfont{title}\insertsectionhead\par%
  \end{beamercolorbox}
  \vfill
  \end{frame}
}

\title{The Title}
\author{The Author}
\institute{The Institute}

\begin{document}

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

\section{Test section one}
\begin{frame}
test frame for section one
\end{frame}

\section{Test section two}
\begin{frame}
test frame for section two
\end{frame}

\end{document}

This is great except that I am using the Frankfurt theme, so the title of each section is going into the top bar. My question: How do I get the long titles in the boxes at the start of each section but have a shortened phrase as the top bar "title"? Thanks.

This question is a follow-up to: Creating sections each with title pages in beamers slides

Answer 1

Instead of \insertsectionhead, you can use \secname for the boxes at the beginning of each section; also, use the optional argument for \section to provide a short version for the navigation bar in the headline:

\documentclass{beamer}
\usetheme{Frankfurt}

\AtBeginSection[]{
  \begin{frame}
  \vfill
  \centering
  \begin{beamercolorbox}[sep=8pt,center,shadow=true,rounded=true]{title}
    \usebeamerfont{title}\secname\par%
  \end{beamercolorbox}
  \vfill
  \end{frame}
}

\title{The Title}
\author{The Author}
\institute{The Institute}

\begin{document}

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

\section[Test section one]{Test section one with a really reallly long title}
\begin{frame}
test frame for section one
\end{frame}

\section[Test section two]{Test section two with a really reallly long title}
\begin{frame}
test frame for section two
\end{frame}

\end{document}

An image of the frame at the beginning of the first section showing the long full title in the box and the short version in the navigation bar.