I am using the tikzposter package and am fairly happy with it except for one small thing: When I have an equation with a sum the sum becomes ridiculously small.

I have read the questions about displaystyle vs textstyle and am using amsmath. Putting \displaystyle in front of \sum doesn't change anything.
Does anyone have any idea how to get a "normal" sum symbol?
MWE:
\documentclass[25pt, a0paper, portrait]{tikzposter}
\usepackage[utf8]{inputenc}
\usepackage{graphicx}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{amsmath}
\usepackage{amssymb}
\title{lalala}
\begin{document}
\maketitle
\block{test}{
\begin{equation*}
\Psi = \displaystyle\sum^{n_{max}}_{n=1}C_n
\end{equation*}
}
\end{document}

cmexhas not been made available at properly large sizes. as i am not a user oftikzposter, and it's not installed on the system i work on, i can't test. but you might try adding\usepackage{exscale}which expands upward the range of sizes in which this font is available. – barbara beeton Jun 26 '15 at 14:21eqnarray. For a single equation such as that, useequation*. – Torbjørn T. Jun 26 '15 at 16:00\usepackage{exscale}doesn't help, but after some digging around I found out that removing\usepackage{lmodern}does. – fifaltra Jun 26 '15 at 16:03