[Tex/LaTex] Beamerposter not showing correct fonts in math mode

beamerbeamerposterfonts

I am making a poster using beamer package and I have problems in mathematical symbols like summation and fractions. My preamble file has following 

\documentclass[final]{beamer}
 \usepackage[scale=1.24]{beamerposter} 
 \usetheme{confposter} 
 \usepackage{graphicx}
 \usepackage{booktabs}
 \usepackage{mathtools}
 \usepackage{amsmath}

These equations give me problems 

\begin{equation}
V(\phi) =  \sum\limits_{m=1}^{n} \left(\sfrac {1}{2} V_m ( 1 - \cos k \phi) \right) 
\end{equation}

 \begin{equation}
 \frac{\mathrm d^2}{\mathrm d^2 x} \left( V(\phi) \right) = \sum\limits_{m=1}^{n}     \left(\sfrac {1}{2} V_m^2 ( \cos k \phi) \right)
 \end{equation}

For instance I need large summation and small fractions. but I am not getting it right.

What I am actually using is the template given in this link, since I am new to LATEX.
http://www.latextemplates.com/template/jacobs-landscape-poster
You can put this modified equations to this templates to test that.
If you need my code I can provide but still based on this template.

Best Answer

You need to load the exscale package after lmodern has been read in. This is a common problem when needing these fonts at large sizes, see the discussion on the TeX FAQ at http://www.tex.ac.uk/cgi-bin/texfaq2html?label=exscale.

Incidentally your code snippet is missing the xfrac package for the \sfrac command. However, as egreg correctly says this looks bad and is ambiguous. Perhaps you mean \tfrac instead - this is what I have now used.

Sample output

\documentclass[final]{beamer}

\usepackage[scale=1.24]{beamerposter} 
\usetheme{confposter}
\usepackage{exscale}
\usepackage{graphicx}
\usepackage{booktabs}
\usepackage{mathtools}
\usepackage{amsmath}

\newlength{\sepwid}
\newlength{\onecolwid}
\newlength{\twocolwid}
\newlength{\threecolwid}
\setlength{\paperwidth}{48in} % A0 width: 46.8in
\setlength{\paperheight}{36in} % A0 height: 33.1in
\setlength{\sepwid}{0.024\paperwidth} % Separation width (white space) between columns
\setlength{\onecolwid}{0.22\paperwidth} % Width of one column
\setlength{\twocolwid}{0.464\paperwidth} % Width of two columns
\setlength{\threecolwid}{0.708\paperwidth} % Width of three columns
\setlength{\topmargin}{-0.5in} % Reduce the top margin size

\title{Unnecessarily Complicated Research Title} % Poster title

\author{John Smith, James Smith and Jane Smith} % Author(s)

\institute{Department and University Name} % Institution(s)

\begin{document}

\begin{frame}

  \begin{columns}
    \begin{column}{0.5\textwidth}
      \begin{equation}
        V(\phi) =  \sum\limits_{m=1}^{n} \left(\tfrac {1}{2} V_m ( 1 -
          \cos k \phi) \right)  
      \end{equation}

  \begin{equation}
    \frac{\mathrm d^2}{\mathrm d^2 x} \left( V(\phi) \right) =
    \sum\limits_{m=1}^{n} \left(\tfrac {1}{2} V_m^2 ( \cos k \phi)
    \right) 
  \end{equation} 
\end{column}
\end{columns}
\end{frame}

\end{document}
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