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% Copyright 2007 by Till Tantau
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\section{Creating Transparancies}

\label{section-trans}
\label{trans}

The main aim of the \beamer\ class is to create presentations for
beamers. However, it is often useful to print transparencies as
backup, in case the hardware fails. A transparencies version of a talk
often has less slides than the main version, since it takes more time
to switch slides, but it may have more slides than the handout
version. For example, while in a handout an animation might be
condensed to a single slide, you might wish to print several slides
for the transparency version.

In order to create a transparencies version, specify the class option
|trans|. If you do not specify anything else, this will cause
all overlay specifications to be suppressed. For most cases this will
create exactly the desired result.

\begin{classoption}{trans}
  Create a version that uses the |trans| overlay specifications.
\end{classoption}

In some cases, you may want a more complex behaviour. For example, if
you use many |\only| commands to draw an animation. In this case,
suppressing all overlay specifications is not such a good idea, since
this will cause all steps of the animation to be shown at the same
time. In some cases this is not desirable. Also, it might be desirable
to suppress some |\alert| commands that apply only to specific
slides in the handout.

For a fine-grained control of what is shown on a handout, you can use
\emph{mode specifications}. They specify which slides
 of a frame should be shown for a special version, for example for the
handout version. As explained in
Section~\ref{section-concept-overlays}, a mode specification is written
alongside the normal overlay specification inside the pointed
brackets. It is separated from the normal specification by a vertical
bar and a space. Here is an example:
\begin{verbatim}
  \only<1-3,5-9| trans:2-3,5>{Text}
\end{verbatim}
This specification says: ``Normally (in |beamer| mode), insert the
text on slides 1--3 and 5--9. For the transparencies version, insert
the text only on slides 2,~3, and~5.'' If no special mode specification is
given for |trans| mode, the default is ``always.'' This causes the
desirable effect that if you do not specify anything, the overlay
specification is effectively suppressed for the handout.

An especially useful specification is the following:
\begin{verbatim}
  \only<3| trans:0>{Not shown on transparancies.}
\end{verbatim}
Since there is no zeroth slide, the text is not shown. Likewise,
\verb!\alert<3| trans:0>{Text}! will not alert the text on a
transparancy.

You can also use a mode specification for the overlay specification
of the |{frame}| environment as in the following example.
\begin{verbatim}
\begin{frame}<1-| trans:0>
  Text...
\end{frame}
\end{verbatim}
This causes the frame to be suppressed in the transparancies
version. Also, you can restrict the presentation such that only
specific slides of the frame are shown on the handout:
\begin{verbatim}
\begin{frame}<1-| trans:4-5>
  Text...
\end{frame}
\end{verbatim}

It is also possible to give only an alternate overlay
specification. For example, |\alert<trans:0>{...}| causes the
text to be always hilighted during the presentation, but never on the
transparancies version. Likewise, |\frame<trans:0>{...}| causes the
frame to be suppressed for the handout.

Finally, note that it is possible to give more than one alternate
overlay specification and in any order. For example, the following
specification states that the text should be inserted on the first
three slides in the presentation, in the first two slides of the
transparency version, and not at all in the handout.
\begin{verbatim}
  \only<trans:1-2| 1-3| handout:0>{Text}
\end{verbatim}

If you wish to give the same specification in all versions, you can do
so by specifying |all:| as the version. For example,
\begin{verbatim}
\frame<all:1-2>{blah...}
\end{verbatim}
ensures that the frame has two slides in all versions. 





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