# Piecewise highlighting in beamer presentation

I would like to do the following with beamer: All items of an itemize environment should be displayed in gray. The current item should be highlighted in black while all others remain grayed out, but visible (So for the example I would like to get three slides in the end: "Hallo" in black on slide 1, the rest in gray; "Welt" in black on the 2nd slide, all other items in gray, etc.). I just went through the manual, could not find any specific code to do so.

\documentclass{beamer}
\begin{document}
\frame{
\begin{itemize}
\item Hallo
\item Welt
\item Foobar
\end{itemize}
}
\end{document}

-

\documentclass{beamer}
\begin{document}
\frame{%
\setbeamercolor{normal text}{fg=gray,bg=}
\usebeamercolor{normal text}
\begin{itemize}
\end{itemize}
}
\end{document}

-
That did the trick. It highlights only the current item and grays out all other. From the "how to present best" point of view Daniel's solution may however be more acceptable. –  Uwe Ziegenhagen Dec 26 '11 at 17:54

The answer involves two things. You'll need to tell beamer which slides to highlight the text on, and that unhighlighted text should be transparent.

\documentclass{beamer}
\begin{document}
\setbeamercovered{transparent}
\frame{
\begin{itemize}
\item<1> Hallo
\item<2> Welt
\item<3> Foobar
\end{itemize}
}
\end{document}

-
Note, Daniel beat me to it, so send credit his way. I'll delete this soon. –  qubyte Dec 26 '11 at 9:17
Mark, I don't think that you should delete your answer. It already got some votes and shows a different syntax. Beamer's overlay stuff is just like that :-) –  Daniel Dec 27 '11 at 14:34

The piecewise uncovering is described in §23 of the beamer user guide ("How to Uncover Things Piecewise"). To have the not (yet) uncovered items "dimmed" instead of invisible, you just need to combine this with a respective "transparency effect", discussed in §17.6 ("Transparency Effects").

The \setbeamercovered{transparent} can also be applied outside of a frame environment to have it's effect global.

\documentclass{beamer}
\begin{document}

\frame{
\setbeamercovered{transparent}
\begin{itemize}[<+->]
\item Hallo
\item Welt
\item Foobar
\end{itemize}
}
\end{document}

-
Aw, damn. You beat me by about 2 seconds. I think Uwe was asking for a single item at a time to be highlighted however. If that is so and you put it in as an update to this answer, I'll remove mine. –  qubyte Dec 26 '11 at 9:15